Plant Unit

Plant Behavior

Growth towards the sun

Plant roots accelerate growth to travel to patches of nutrients

Plant roots slow down when passing nutrients for efficiency

No Roots

Producing it's own food

Obligate Parasites lives off host

Knows which plant it likes more

Protection

Tobacco plant uses nicotine poisons to induce seizures, paralysis, adn morality

When preyed on it will releases SOS signal that predators will take care of

Vascular vs Non-Vascular

A vascular plant has specialized tissue that helps to transport water and nutrients Most plants are vascular to transport
water and nutrients(xylem and phloem)
Have roots, leaves and stems

ability to live away from major water sources e.g. ponds, lakes

Ex. Flowers, trees, shrubs and grasses

Non Vascular

No system of vessels to transport water and
nutrients (xylem and phloem)

No true leaves, roots or stems

Depend on diffusion, osmosis and active transport to get nutrients

Need to grow close to water (for reproduction and growth)

Grow close to the surface and when they die they leave soil for plants to grow

Seeded vs. Seedless

Seeded plants contain an embryo surrounded by a seed coat. Inside the seed is nutrients that help feed it as it grows.

Seedless

Seedless plants do not have seeds and are spread by windblown spores. They tend to live in moist areas and examples include ferns and horsetails.

Gymnosperm vs. Angiosperm

Gymnosperm

Most have long, thin needles (these are their leaves)

Most are cone bearing

Do not produce seeds or fruit

Requires pollen to produce

Generally trees

Tend to be found in harsh environments, found worldwide

Wide spread root systems (anchor themselves and helps to get nutrients)

Angiosperm

Often called flowering plants (but not all of them are flowering plants)

Plants bear fruits

Fruits are designed to disperse seeds

Play a large role in feeding people

Best adapted to the various climates on Earth

Most abundant plant form on Earth

Adaptations

Arctic

mosses, lichens, trees and shrubs live here

Roots are shorter and the plants are shorter

built in antifreeze to withstand the cold

faster lifecycle to take advantage of the limited sunlight

Desert

Long shallow root systems

Catci are capable to storing large quantities of water e.g. 6 m tall cactus can store 400 L of water

Have accordion pleats to allow the plant to expand

Spines prevent predators from getting to the water

Waxy skin to reduce water loss

Rainforest

great competition for pollinators by use of complex flower structures and scents

competition for sunlight results in some plants called epiphytes that grow on trees with trailing roots such as orchids, some mosses and ferns

some plants do not obtain enough nutrients from the soil and consume insects such as the Venus fly trap and the pitcher plant

Primary Succession

Establishes a community in an area of exposed rock that does not have topsoil

i.e. after glacial retreating, cooled lava, geologic upheaval

Plants compete for light and space, some species better able to survive in changing environment

Climax community is the final stage of ecological succession. i.e. mature oak/hickory forest

Secondary Succession

It is the recolonization of an area after an ecological disturbance in which the soil remains in tact.

Often seeds and roots remain, some seeds will only germinate after a fire i.e. Jack or Lodge pine

Ecological Disturbances

They are frequent and important

Provide opportunities for other plant growth

i.e Fallen trees open spaces in the canopy, allow shade intolerant plants the opportunity to establish themselves

The greater the plant diversity in an ecosystem, the more resilient the ecosystem is to disturbances

Terms

The ability to detect change and to respond is called sensitivity.

Response is a form of defence that allows organisms to survive.

Plant adapt to new situations by modifying their growth, by means of chemicals called growth regulators[hormones].

Nastic Response: A plant’s movement in response to a stimulus that is not associated with the direction of the stimulus

Tropism: A plant’s growth response to external stimulus coming from one direction in the environment

Tropism

Phototropism

Phototropism is a growth response of a stem towards light, so that it can receive the maximum amount of light for photosynthesis

Less auxins produced on the side of the plant towards the light

Gravitropism

Gravitropism is a plants natural growth response to the effects of gravity

The roots demonstrate positive response by growing towards gravitational pull

The stem demonstrates negative response by growing against gravity

Plant’s response will be to return to the upward position

Thigmotropism

Thigmotropism is the growth of a plant in response to contact

The side of a plant in contact with a surface of a stimulus will produce auxins on the non-contact side, producing growth

The response will continue resulting in a “winding” effect

Growth

Limit growth

Author

Publishing information

Availability

Kill weeds

Author

Publishing information

Availability

Away from light

Author

Publishing information

Availability

Not grow as much

Author

Publishing information

Availability

herbicides

Excessive growth to kill

Auxins

cytokinins

Gibberellins

spoiled

raspberry spoiling others

one spoiled

released ethylene gas

ethylene gas causes all other to ripen

Able to survive harsh conditions

Two Types of Systems

Open Transport System

blood bathes the cells directly
Moves through muscle contractions

Closed Transport System

blood is pumped around the body in a network of vessels (for collection, distribution and exchange)
blood circulates in only one direction
Gases and nutrients must pass through walls of blood vessels to reach cells

circulatory system

Pulmonary Circulation

transports oxygen-poor blood from the right ventricle to the lungs where blood picks up a new oxygen supply. Then it returns oxygen rich blood to the left atrium.

Systemic Circulation

Systemic circulation provides a functional blood supply to all body tissue.

It carries oxygen and nutrients to the cells.

It picks up carbon dioxide and waste products.

Blood enters the R atrium and passes through the right ventricle.

The R ventricle pumps the blood to the lungs where it becomes oxygenated.

The oxygenated blood is brought back to the heart by the pulmonary veins which enter the L atrium.

From the L atrium blood flows to the L ventricle.

The L ventricle pumps blood to the aorta which distributes the oxygenated blood throughout the rest of the body.

Blood Vessels

Arteries

Carry blood away from the heart

Carry oxygenated blood

Have thicker walls because the pressure in the arteries is highe

Veins

Carry blood from the body towards the heart

Carry deoxygenated blood

Capillaries

Site of gas, waste, and nutrient exchange

Very thin, small red blood cells travel in single file in capillaries

Blood

Plasma

92% water. It transports blood solids, nutrients, hormones, and other materials.

Red Blood Cells

carry oxygen to cells and carbon dioxide away from them.

White Blood Cells

help fight disease and infection by attacking germs that enter the body.

Platelets

help blood form a clot at the site of a wound. A clot seals a cut and prevents excessive blood loss.

Blood Pressure

Systolic Pressure

as your heart contracts to push blood into your arteries, your blood pressure is at its highest point.

Diastolic Pressure

As your heart relaxes to refill, blood pressure is at its lowest point.

Problems of the Circulatory System

Anemia is an abnormally low level of hemoglobin, a protein that binds to oxygen in red blood cells.

Leukemia is a disease in which extra white blood cells are produced.

Hemophilia is a disease in which the blood plasma does not contain substances that help the blood to clot.

Hypertension: is a condition in which blood pressure is consistently higher than normal, which can lead to heart attack, stroke, or kidney failure.

Stroke usually results from blood clots that block vessels in the brain, or from the rupture of a blood vessel.

Heart Attack is a blockage of the flow of blood to the heart.

Composition of Air We Breathe

78% Nitrogen (N2)

21% Oxygen (O2)

1% CO2 and Trace Elements (e.g., Argon)

Human Adaptations

1. Water must be present at the respiratory surface(moist enviornments allows for gases to dissolve in water)

2. The respiratory surface must be large( inorder to exchange oxygen and carbon dioxide quickly enough to meet the body’s needs)

Upper Respiratory

Nose and Mouth

Pharynx

Connects nasal and oral cavity to larynx

Cilia in top portion move food towards mouth to be swallowed

Epiglottis

A flap that prevents food from entering the lungs by blocking the glottis (opening of trachea)

Small, flexible flap of tissue

Larynx

Contains the vocal chords – for sound, aka “voice box”. Opening to lungs

Two flaps of cartilage, vibrate when air passes through

“Adam’s Apple” – a thick band of cartilage that surrounds and protects the larynx.

Trachea

Passage of air into 2 bronchi, “windpipe”.

Filter particles

~10-12cm long

Semicircular cartilage rings to prevent collapse -Cilia and mucus

Lower Respiratory

Bronchi

One goes to each lung.

Each carries air into lungs and splits into many bronchioles

Full cartilage rings for support

Bronchioles

Many branches carry air to alveoli

Able to change diameter to regulate air flow

Many branched tubes, smallest passageways, to increase surface area

Smooth muscle walls

NO cartilage rings

Aveoli

Site of external respiration (gas exchange).

~150 million per lung!

Very thin tiny sacs (large surface area).

Single cell layer, surrounded by capillaries.

Coated with “surfactant” (a lipoprotein) to prevent sticking.

Pleural membrane

Surrounds lungs and lines chest cavity

Reduces friction between lungs and chest cavity

Filled with fluid that reduces friction between lungs and chest cavity during inhalation

Diaphragm

Increases and decreases volume of chest cavity

Dome shaped, thin, muscular

Endoscopes

Used to detect abnormalities in the small intestine (ex: tumors, bleeding)

Lasers

Surgery that can help change the shape of the eye and its focal point

Laser breaks down bonds or organic material in the eye so that the surgeon can reshape the cornea

Risks (not high): blurry vision, partial or complete blindness

Magnetic Resonance Imagining (MRIs)

Magnetic resonance imaging

4 parts :

Magnets: causes water molecules to line up in one direction and spin around to give off energy

Antenna: detects radio signals given off by the water molecules

Computer: collects data picked up by the antenna

Software: creates pictures out of the data

Takes many x rays form different angles to create a 3D image of your internal body

A contrast medium will be injected to enhance imaging

A radiopharmaceutical is injected and concentrates in the disease areas

Allows us to look into the body and make appropriate diagnosis and treatment decisions

Arthroscopic Surgery

Small incision, minimally invasive , less scarring, quicker recovery

Used to fix ligaments, repair tendons

Viewing internal anatomy using high frequency sound waves

A transducer is placed on the body which emits sound waves. These sound waves reflect off structures and interpreted by a computer which displays an image

Computer software used in viewing 3D models of

Modelling consists of 3 phases:

Using a CT scanner, images are taken

Walking in a lab attached to infrared markers on pelvis and knees

Images and data from the body’s movement is combined with computer software to create a 3D model

Organic compounds

Lipids

Examples:are fats, oils, and waxes.

Lipids are energy dense, containing 9 calories per gram.

Lipids are used for storing energy, making cell membranes, and synthesizing steroid hormones.

Carbohydrates

Sugars and starch are the carbohydrates that humans can digest. “Fiber” is indigestible carbohydrates, such as cellulose and inulin.

Glucose is needed by all body cells as energy. Nerve cells must have glucose to operate.

Examples: fructose, lactose, cellulose, glycogen, maltose, glucose

Proteins

Amino acids from digested proteins are used by cells to build all the proteins that our body needs. Proteins provide structure and support, speed up chemical reactions, provide immunity, transport ions

Examples: insulin, enzymes, hemoglobin, collagen, antibodies

Minerals

Sodium, potassium, zinc, iron, calcium,magnesium among the minerals that humans need.

Most minerals can be found in whole grains, fruits, vegetables, nuts, and meats. Highly processed foods may be deficient.

Vitamins

Vitamins play many different roles in metabolism.

We do not obtain energy from vitamins; however, some vitamins are necessary to run energy-related processes in cells.

Supplies body with energy and raw materials for synthesis of chemical compounds.

Nutrients aid in GROWTH, MAINTENCE and REPAIR of tissues.

Digestion

Types of Digestion

Physical/Mechanical: is the act of breaking down food into smaller pieces using teeth (mastication), as well as contractions of the stomach.

Chemical: enzymes and water break down food so that it can eventually be absorbed by body cells.

4 Stages in Digestion

1. Ingestion

The taking in of nutrients

2. Digestion

The breakdown of complex organic molecules into

smaller components by enzymes.

3. Absorption

The transport of digested nutrients to tissues of the body.

4. Elimination

The removal of waste food materials from the body.

Teeth

incisors: specific for cutting

canine: sharp for tearing

pre-molars: grinding

molars: crushing

Used for mechanical/physical digestion
(mastication). They are necessary for
breaking food into smaller particles.

Tongue

Strong muscle.

Has taste buds.

Helps swallow (movement of food)

Saliva

Fluid secreted by salivary glands

Contains amylase which breaks down complex to simpler carbohydrates

Lubricates food to be swallowed

Dissolves food particles

At this point food can be “tasted”

2. Pharynx:

Swallowing (gag/swallow reflex)

Divides food and air

3. Epiglottis:

Covers the trachea

Protects / prevents food from entering the windpipe.

4. ESOPHAGUS

Peristalsis: rhythmic, wavelike contraction of smooth muscle that moves food through the esophagus

5. STOMACH

J-Shape organ that can store up to 1.5 L of food

Movement of food in and out of stomach is regulated by sphincters

Esophageal sphincter: regulates food from esophagus (acts like a valve)

Pyloric sphincter: regulates food from stomach to small intestine

juices

Gastric juice

Hydrochloric acid (HCl) mucus, pepsinogens and other materials

Pepsinogens

enzymes that when exposed to a low pH (1-3) such as conditions in the stomach, turns into its active form pepsin which is a enzyme the digests proteins

Food broken down into chyme(thick liquid).

6. SMALL INTESTINE

3 Parts

Duodenum: most digestion occurs here

Jejunum: has many folds that continue breakdown and absorption of remaining proteins and carbohydrates

Ileum: less absorption occurs here, unabsorbed particles are pushed through.

Small Intestine Absorption

nutrients are broken down and absorbed

complex carbohydrates are broken down into simple carbohydrates like glucose with the use of an enzyme called amylase

amylase is produced and released by the pancreas

these simple sugars (monosaccharides) are absorbed into the capillaries of the villus

Proteins

Broken down into amino acids

Trypsin, an enzyme produced and released by the pancreas breaks down polypeptides into amino acids

Amino acids are absorbed into the capillaries of the villus

Fats

Are physically broken down from large fat droplets into smaller fat droplets with the use of bile

Bile is produced by the liver and stored in the gall bladder

Bile is chemically digested with the use of lipase

Lipase is an enzyme produced and released by the pancreas

Lipase is broken down into absorbable fat that enters the lacteals of the villi in the small intestine

7. LARGE INTESTINE

Wider and shorter than the small intestine.

Cecum – storage (chyme); ends with appendix.

Colon is largest part of large intestine; stores waste so that water as well as some inorganic salts, minerals and vitamins can be absorbed.

Liver

Produces bile for physical digestion of lipids.

Removes excess sugar from blood and stores it.

Responsible for detoxifying blood (ex. Alcohol)

Recycles damaged red blood cells

Gall Bladder:

Stores bile (if stomach empty)

Releases bile when chyme is present in the small intestine.

Absorption

Villi: small finger-like projects that extend into the small intestine which increase surface area for absorption.

Microvilli: are a microscopic projection on cell membrane

Lacteals: are small vessels that transport fat to the circulatory system

Elimination of Wastes

Rectum

Chemical digestion is finished at the large intestine.

Collects waste for excretion.

Anus: Controls discharge of waste (feces).

12 AM to 5AM

Heavy Bombardment Period

Catastrophic beginning with lots of collisions (ie. Mars sized object hit the Earth to form our Moon)

Atmosphere filled with carbon dioxide and hydrogen sulfide

Earth was frequently hit by asteroids and meteors

This period of time was thought t o aid in the formation of amino acids

No oceans

First Life Forms

Though to first evolve 3.8 Billions of years ago

Archaebacteria

Bacteria capable of living in extreme environments

Various types of archaebacteria such as:

Acidophiles – can live in acidic environments i.e. snotites and phlegm balls

Methanogens – can live in methane rich environments i.e. the bacteria found in the South African mines

Halophiles – can live in environments that are very salty i.e. dead sea and pink sea salt formed from bacteria

Elements key to life on Earth are present

Carbon, nitrogen, oxygen and hydrogen

5 AM to 1 PM

The heavy bombardment ended

Life was able to move to the surface

Bacteria that had chlorophyll was able to survive and reproduce passing along their trait to the next generation

These bacteria are able to conduct photosynthesis and produce sugar to survive

These bacteria are distant relatives to the cyanobacteria that we find on Earth today

Evidence of this transition can be found with stromatilites found in Western Australia

These bacteria produced oxygen gas as a by-product which filled the oceans with oxygen gas and eventually the air

1 PM to 9PM

Oxygen levels rise from less than 1% to 21%

The increase in oxygen concentration allowed for the formation of the ozone layer

Protects us from harmful ultraviolet radiation from the sun

Increase in oxygen concentration allowed for more complex life forms to thrive as we need more oxygen to perform cellular respiration

Cellular respiration is a process where we take glucose and convert it into ATP (a usable energy molecule for our cells)

9 PM to 11:59 PM

6 minutes after 9 the first multicellular life forms appear on Earth, first it was:

Fish, then

Insects

Reptiles

Dinosaurs

First mammals

Humans (11:59:30)

Variations Within a Species

The variations within a species are the structural, functional, or physiological differences between individuals.

These changes are the result of random, heritable mutations in DNA that accumulate over generations.

Interaction with the environment determines whether a variation is positive or negative for the individual organism.

Adaptation & Survival

Mimicry is a type of structural adaptation. Harmless species physically resemble a harmful species. Predators avoid the harmless species as much as they do the harmful one.

Selective Advantages

A selective advantage is a genetic advantage that improves an organism’s chances of survival in terms of both survival in a changing environment and reproduction.

Evidence from Fossil Records

When an organism dies, it may form a fossil. A fossil is the remains or impression of a prehistoric organism cast in rock. The following data has been collected around the world:

Fossils found in young layers of rock (rock closer to the surface) are more similar to species living today than fossils found in older deeper layers of rock.

Fossils appear in chronological order in the rock layers.

fossil records show that fish are the oldest vertebrates (animals with backbones) and it isn’t until more newer layers of rock do you find other vertebrates (reptiles, mammals, birds, etc.).

Evidence from Anatomy

Homologous structures are those that have similar structural elements and origin but may have different functions.

Vertebrate forelimbs can be used for various functions, such as flying (bats), running (horses and cats), and swimming (whales and seals).

Even though they are used for different functions, they all contain the same set of bones, and are organized in similar ways because they all originated from a common ancestor.

Evidence from Biogeography

Biogeography is the study of the distribution of organisms throughout the world.

Organisms that live closely together are more similar than organisms that live far away but in similar habitats.

For example, cacti are only found in the Americas even though there are deserts in Africa. Since all cacti have a common ancestor, it makes sense that they are located in the same parts of the world.

Also, organisms on islands often closely resemble animals found on the closest continent. Lemurs are only found on Madagascar but there are lemur fossils in India (Madagascar broke off from India 88 million years ago).

Evidence from Embryology

Embryology is the study of the early pre-birth stages of an organism’s development.

Embryology has been used to determine relationships between different organisms.

For example, all vertebrates have similar stages of early embryo development because all vertebrates have a common ancestor.

Evidence from DNA

DNA is the blueprint for an organism and scientists have been able to determine how closely related two organisms are by comparing how similar their DNA is.

We know that organisms pass on DNA to their offspring (children).

If two different organisms have similar patterns in their DNA, then they must have both inherited that DNA from a common ancestor.

For example, humans and chimpanzees have more similarities in their DNA than humans and dogs, so humans and chimpanzees have a more recent common ancestor.

Basic Information

Microevolution is the change in the allele frequency for a population

These changes when sustained over many generations and a long period of time can lead to macroevolution and the creation of a new species

Genes

Genes are segments of DNA that code for a specific trait, such as hair colour, eye colour, height, eyelash length etc.

Whenever we look at any trait, such as hair colour, we have variations of that trait (e.g. red, black, blonde and brown).

These variations of a gene are called alleles.

We have two alleles for each gene. These alleles "work" together in determine what our hair colour, height, eye colour etc will be.

Mutations

Mutations are changes that occur in the DNA of an individual, a heritable mutation has the potential to affect an entire gene pool

The effect of mutations is that they introduce new alleles into a population, which changes allele frequencies

Mutation are the only way that new alleles are introduced into populations

Gene Flow

Gene flow may change allele frequencies in either or both populations through a “flow”, or movement of genes (alleles)

Genetic Drift

Genetic drift is the change in frequencies of alleles due to chance events in a breeding population

Sample size can greatly impact the gene pool of a population - the smaller the population, the more likely that the future generations won’t reflect the parent generation

Think of flipping a coin 1000 times versus 10 times

The Founder Effect

is a change in a gene pool that occurs when a few individuals start a new isolated population

Often, new populations are formed by only a few individuals, or founders

These founders will carry some, but not all, of the alleles from original population

Diversity in the new gene pool will be limited

Occurs frequently on islands

The Bottleneck Effect

is the changes in gene distribution that result from a rapid decrease in the population size

Starvation, disease, human activity, and natural disasters can quickly reduce the size of a large population

Since the survivors have only a fraction of the original population alleles, the gene pool has lost diversity

Non-Random Mating

is the mating among individuals on the basis of mate selection for a particular phenotype or due to inbreeding

The Effect of non-random mating is that it increases the proportion of homozygous individuals in a population

This is in contrast to random mating where breeding partners are randomly selected - the likelihood of specific genotypes mating is based on the allele frequencies within a population

Inbreeding occurs when closely related individuals breed together

Close relatives share similar genotypes, so inbreeding leads to increases in frequency of homozygous genotypes

As homozygous genotypes become more common, harmful recessive alleles are more likely to be expressed

Sexual selection is natural selection for mating based, in general, on competition between males and choices made by females

Often, males and females in a population have drastically different physical characteristics such as colourful plumage in male birds and antlers in male deers - this difference is called sexual dimorphism

Macroevolution: major evolutionary change. The term applies mainly to the evolution of whole taxonomic groups over long periods of time.

Reproductive Isolating Mechanisms

PRE-ZYGOTIC mechanisms that prevent mating or fertilization

Behavioral isolation

two populations do not exchange alleles because they do not respond to each others mating rituals

Temporal Isolation

two populations do not exchange alleles because they are only available to exchange alleles at different times of year or even of the day

Ecological/Habitat Isolation

two populations do not exchange alleles with each other because they are in different geographic places or at different places within the same ecosystem

Mechanical Isolation

two populations do not exchange alleles because they are anatomically incompatible

Gametic isolation

two populations exchange sperm and eggs but rarely fuse to form a zygote

POST-ZYGOTIC mechanisms that prevent development of a zygote

Hybrid inviability

even though the zygote is created, it fails to develop to maturity due to genetic incompatibility

Hybrid sterility

even though the hybrid is healthy and vigorous, it is not able to reproduce

Hybrid breakdown

the first generation hybrids are fertile, but when these hybrids mate, offspring of the next generation are sterile or weak.

Basic info

Development of a new species through a variety of factors

Rate of speciation depends on generation, time, environmental conditions, etc.

can be caused by a change in just 1 gene or a set of genes causing some sort of isolation

Types of speciation

Gene flow is interrupted when a population is divided into geographically isolated subpopulations

Parapatric Speciation

Occurs when part of a population enters a new habitat bordering the range of the parent species

Some gene flow may occur between populations in border zone

Sympatric Speciation

Occurs in populations that live in the same geographic area

Less common than allopatric speciation

Happens when gene flow is diminished by:

Polyploidy

habitat differentiation

Sexual selection

Charles Lyell

Principles of Uniformitarianism

Theory states that geological processes operate at the same rate today as they have in the past

Slow subtle processes that happen over a long period of time lead to substantial changes in the long term

Provided a geological perspective that inspired Darwin

Limitations of Theory

Doesn’t take into account varying geological processes like natural disasters, catastrophes, climate change, impact of human activity

Georges Cuvier

Theory of Catastrophism

Developed Paleontology - the study of ancient life through fossils

Noted that species are found in particular rock layers and that new species appear and disappear over time

Theory of catastrophism states that natural events like floods and volcanic eruptions killed species living in a region and allows species from neighboring areas to repopulate an area, resulting in change

Limitations in Theory

Doesn’t take into account that changes can also be slow and subtle, specifically changes within a population

(other information…)

Discovered that each stratum (layer) of rock held a unique group of fossil species

Discovered that the oldest fossils are in the deepest layer

Suggested that catastrophes killed many species (catastrophism) and that these events corresponded to the boundaries between the fossil strata

Jean-Baptiste Lamarck

Inheritance of Acquired Traits (use and disuse)

Theory states that species increased in complexity over time until they reached a level of perfection

Organisms become increasingly better adapted to their environments

Traits acquired during an organism’s life can passed on to offspring

Body parts that are not used would be lost over time

Limitations of Theory

Doesn’t reflect how we inherit traits

Traits cannot be gained just because they would be useful

Thomas Malthus

- Break or sudden event interrupts

- Leads to selection of those more suited to survive

- May lead to creation of new species if separation continues

Carrying capacity is the sustainable balance achieved between population and environment

Populations are limited by: predators, food, shelter, water, disease, competition

Stephen Jay Gould & Niles Eldredge

Punctuated Equilibrium

That evolution occurs both gradually and in small punctuated events

During periods of stasis change is slow, however, sudden events (punctuated events) i.e. a flood or volcanic eruption can put huge selective pressures on a population requiring a rapid rate of evolution in a short time frame

Charles Darwin

Variation exists within species - mutations are the sources of variations

Selective pressures determine which organisms survive - “survival of the fittest”

Organisms with traits that are better suited will survive, reproduce, and pass on those traits to offspring

Descent with Modification - changes do not demonstrate progress (improvement) - it is simply change

There are three types of natural selection:

1. stabilizing selection

Selects for (favours) average phenotypes

Selects against extreme phenotypes

Results in a decrease of populations genetic variance

2. directional selection

Populations genetic variance shifts towards a new phenotype when exposed to environmental change

Selects for (favours) one extreme phenotype

Selects against other phenotypes

3. disruptive selection

Selects for (favours) 2 extreme phenotypes that each have specific advantages

Select against average or intermediate phenotype because it is less fit than the extremes

Example - mating lobsters

Large lobsters mate by force and small lobsters sneak in female populations in alpha male territory

Recap: Variation in Species

Variation is created by the different combinations of genetic information (alleles) that offspring inherit from their parents.

A mutation is a permanent change in the genetic material of an organism and is the only source of new genetic variation.

Adaptations are the result of a process of gradual, accumulative changes due to mutations, that help an organism survive and reproduce

A selective advantage is a genetic advantage that improves an organism’s chances of survival in terms of both survival in a changing environment and reproduction.

Natural Selection

Natural selection describes the process of change in the characteristics of a population of organisms over many generations.

If an organism produces offspring that also survive to reproduce, that organism is said to be fit for the environment.

to select for certain characteristics in some individuals and select against certain characteristics in others

temperature change

light level change’

change in predators

change in competition

Artificial Selection

Artificial selection is a selective pressure exerted by humans on populations in order to improve or modify particular traits.

cows bred to increase muscle for meat consumption

chickens bred to produce more eggs

Charles Darwin

Information

Father of Evolution

Proposed a mechanism for evolution, natural selection

Darwin went on a 5-year trip around the world on the ship, the HMS Beagle

As the ship’s naturalist, he made observations of organisms in South America and the Galapagos Islands

Wrote a book called “The Origin of Species” to propose his theory of natural selection, which is a mechanism for evolution

Darwin’s Observations

The flora and fauna were different in different regions.

Finches found on islands resembled continental finches but were different in some characteristics.

Finch beaks were adapted to the food source on each island.

Darwin’s Questions

Why were all types of organisms not randomly distributed?

Why would living and fossilized organisms that looked similar be found in the same region?

Why did the Galapagos species so closely resemble organisms on the adjacent South American coastline?

Could species have been modified from an ancestral form that arrived on the Galapagos Islands shortly after the islands were formed?

Evolution by Natural Selection

Overproduction

More individuals are born than can be sustained by their environment, which creates a struggle for existence

Variation

Each individual has a unique combination of inherited traits.

Adaptation: an inherited trait that increases an organism’s chances of survival

Since the environment changes….

The more variation of types of species in an habitat, the more likely at least some will survive

EX: Dinosaurs replaced by mammals

Competition

Individuals COMPETE for limited resources:

Food, water, space, mates

Natural selection occurs through “Survival of the fittest”

Fitness: the ability to survive and reproduce

Not all individuals survive to adulthood

Selection

The individuals with the best traits / adaptations will survive and have the opportunity to pass on it’s traits to offspring.

Natural selection acts on the phenotype (physical appearance), not the genotype (genetic makeup)

Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

Individuals with traits that are not well suited to their environment either die or leave few offspring.

Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals.

Descent with Modification

Darwin believe that all life has one common origin, and from that origin life diversified to the forms that we see on Earth today.

Natural selection does not demonstrate progress, but merely results from the ability of species to survive local conditions and to pass on the traits that helped them survive.

Each living species has descended, with changes, from other species over time.

Change does not demonstrate progress (improvement)...it is simply change.

One Origin, Three Paths of Evolution

Over time, evolution can follow many different paths

An evolutionary pattern where two species become increasingly different

Result of differing selective pressures or genetic drift

Often happens when two closely related species diversify to new habitats

On a large scale, divergent evolution is responsible for the creation of the current diversity of life on earth from the first living cells.

On a smaller scale, it is responsible for the evolution of humans and apes from a common primate ancestor

Occurs when divergent evolution occurs in rapid succession, or simultaneously, among a number of populations

Species “radiates out” from common ancestor

One original species gives rise to three or more species.

Commonly occurs after mass extinction

Convergent

An evolutionary pattern when two or more species become increasingly similar in phenotype in response to similar selective pressures

species of different ancestry begin to share analogous (similar in appearance but different evolutionary origins) traits because of a shared environment or other selection pressure

Coevolution

Used to describe cases when two (or more) species reciprocally affect each other’s evolution

The evolution of the morphology of a plant may affect the morphology of a herbivore that eats that plant, which may affect the evolution of the plant, which might affect the evolution of the herbivore and so on, and so on

Predator/prey and parasite/host

Competitive species

Mutualistic species

DNA must replicate so that during cell division, the new cells formed each receive a complete set of genetic information

Reproduction (e.g. unicellular organisms)

Growth (e.g. 1 fertilized egg --> human of ~100 trillion cells)

Healing and tissue repair

Mitosis & the Cell Cycle

Mitosis occurs when a parent cell divides to produce two identical daughter cells

Mitosis refers to the process of dividing the nuclear material

Cytokinesis refers to the process of separating the cytoplasm and its contents into equal parts

The cell cycle consists of mitosis, cytokinesis and interphase

G1 phase: cell grows

S phase: DNA is replicated

G2 phase: cell prepares for mitosis

DNA is visible in the nucleus as strands called chromatin

Centrioles move to opposite poles of the cell

Chromatin condenses and shortens into chromosomes

Spindle fibres form between the centrioles

Nuclear membranes starts to disappear

Spindle fibres attached to centromeres pull chromosomes into place

Chromosomes line up across the equator of the cell

Centrioles duplicate

Chromatids separate at the centromere

Single-stranded chomosomes are pulled to opposite poles by spindle fibres contracting

Two nuclear envelopes form

Single-stranded chromosomes uncoil to become chromatin

Cytokinesis occurs after telophase:

Organelles are distributed between the two daughter cells and the cell membrane pinches inward

Meiosis vs Mitosis

The purpose of mitosis is to maintain genetic continuity (the number of chromosomes in each daughter cell stays the same)

The purpose of meiosis is to produce gametes (sex cells) which unite during sexual reproduction (the number of chromosomes in each sex cell is half of parent cell)

Asexual & Sexual Reproduction

Asexual

Asexual reproduction is any reproduction that does NOT involve meiosis.

1. A single parent gives rise to offspring that are genetically identical to the original parent (clones)

2. Often produces many offspring rapidly

3. There are no specialized structures required by the parent.

Sexual

Sexual reproduction is any reproduction that does involve meiosis.

Genetic information from parent cells are combined to produce a new organism

(offspring are genetically different from parent)

Requires more energy and time than asexual reproduction

Sexually reproducing organisms are better able to adapt to changing environments because of differences between individuals

Individuals that are better adapted will survive and perpetuate the species

Somatic Cells and Gametes

Somatic Cells are “body” cells and contain the normal number of chromosomes ….called the “Diploid” number

Gametes are the “sex” cells and contain only ½ the normal number of chromosomes…. called the “Haploid” number (the symbol is n)….. Sperm cells and ova (egg) are gametes.

The Male Gamete is the Sperm and is produced in the male gonad the Testes

The Female Gamete is the Ovum (ova = pl.) and is produced in the female gonad the Ovaries

During Ovulation the ovum is released from the ovary and transported to an area where fertilization, the joining of the sperm and ovum, can occur.

Fertilization, in Humans, occurs in the Fallopian tube.

Fertilization results in the formation of the Zygote. (fertilized egg)

The fusion of a sperm and egg to form a zygote.

A zygote is a fertilized egg

If an organism has the Diploid number (2n) it has two matching homologues per set.

One of the homologues comes from the mother (and has the mother’s DNA).… the other homologue comes from the father (and has the father’s DNA).

Most organisms are diploid. Humans have 23 sets of chromosomes,

Homologous Chromosomes

Pair of chromosomes (maternal and paternal) that are similar in shape and size.

Homologous pairs (tetrads) carry genes controlling the same inherited traits.

Each locus (position of a gene) is in the same position on homologues.

Humans have 23 pairs of homologous chromosomes.

22 pairs of autosomes

1 pair of sex chromosomes

Autosomes

(The Autosomes code for most of the offspring’s traits)

In Humans the “Autosomes” are sets 1 - 22

Sex Chromosomes

The Sex Chromosomes code for the sex of the offspring.

** If the offspring has two “X” chromosomes it will be a female.

** If the offspring has one “X” chromosome and one “Y” chromosome it will be a male.

Dihybrid Crosses

Incomplete dominance

In Incomplete Dominance, every genotype has its own phenotype. (One allele not completely dominant over the other.) Third phenotype that is a blending of the parental traits. (2 alleles produce 3 phenotypes.)

Result: Heterozygous phenotype somewhere in between homozygous phenotype.

co-dominance

Both alleles contribute to the phenotype.

Example: In come chickens

Black Chicken x White 🡪 Speckled Chicken

When Chromosomes do not divide correctly in meiosis

Results in gametes with incorrect number of chromosomes

The sex of an individual is determined by the sex chromosomes contributed to the zygote by the sperm and the egg

An egg can donate an X

A sperm can donate an X or Y

Therefore the sperm determines the sex of a child

Some traits are located on the sex chromosomes, so the inheritance of these traits depends on the sex of the parent carrying the trait.

Most known sex-linked traits are X-linked (carried on the X chromosome). This is probably because the X chromosome is much larger than the Y chromosome.

SEX-LINKED DISORDERS

Some sex-linked traits are associated with disorders.

Most are found on the X chromosome, Y-linked disorders are rare.

Males are at a much greater risk for inheriting sex-disorders because they only inherit one X, so if the X has the allele for the disorder, they will suffer from the disorder.

Recessive lethal X-linked traits result in death.

DNA

Although environment has some impact on the traits of an organism, DNA has the final word.

DNA achieves control because it determines the structure of proteins.

All living things contain proteins and all the actions of living things depend on proteins called enzymes.

DNA Structure

DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix.

A molecule of DNA is made up of millions of tiny subunits called Nucleotides.

Each nucleotide consists of:

Phosphate group

Pentose sugar

Nitrogenous base

DNA and Genes

A gene is a section of DNA that codes for a protein.

Each unique gene has a unique sequence of bases.

This unique sequence of bases will code for the production of a unique protein.

It is these proteins and combination of proteins that give us a unique phenotype.

A cattail, a cat and a catfish are all different organism composed of proteins with the same 4 nucleotides. The difference?

SEQUENCING

SANTA and SATAN same letters different order

Order matters!

Each cell in the body has a copy of DNA that was present in the original fertilized egg of the zygote.

Before the cell can divide it first makes a copy of its chromosomes through DNA replication

ALL organisms undergo DNA replication.

From DNA to Protein

Sequencing of nucleotides in DNA contain information.

This information is put to work through proteins.

Proteins fold into complex 3-D shapes and become key regulators – forming muscle tissue, enzymes and controlling chemical reactions.

DNA does not leave the nucleus.

So how does DNA get its message to the rest of the body?

DNA needs a messenger to travel to the cell (ribosomes via rough ER) to make a protein and then the protein can travel all over the body.

THE MESSENGER =mRNA

RNA

RNA differs from DNA in 3 ways:

Single stranded vs. double stranded

Ribose sugar vs. deoxyribose

Contains URACIL(U) vs. of thymine (T)

Translation to Proteins

mRNA leaves the nucleus with the code for the protein

Remember CODONS? (the sets of 3 that DNA is arranged in)

These code for Amino acids

There are 20 possible combinations and as a result 20 amino acids

There are also STOP codons and START codons

Nucleotide sequence transcribed from DNA to mRNA is the genetic message. The complete info for life.

20 AA act like the alphabet for DNA (26 letters make millions of words.)

64 possible combinations of the 20 AA.

Similar to a computer binary code 001100101000111110

Genetic Changes

Mutations- caused by errors in replication, transcription, cell division or by external agents.

A mutations in reproductive cells means the gene becomes part of the organism and can result in:

New trait

Non working proteins

Structural or functional problems

Death of the organism

Mutations in body cells:

Not passed to offspring but may be harmful to the individual

Impaired function of the cell (loss of function) or impaired cell division (cancer)

Point mutation- One change in a nucleotide can change the entire meaning.

The dog bit the cat.

The dog bit the car.

Frame-Shift Mutation - A single base pair is added or deleted. The entire strand shifts over. Entire protein is changed.

Chromosomal Alterations

May occur in meiosis.

Part of chromosome may be lost

Very common in plants, but can happen in all organisms

Homologous chromosomes do not pair or separate correctly: Down’s Syndrome.

Few mutations resulting in chromosomal alterations actually are passed on because Zygote often dies

Causes of Mutations

May be Spontaneous

Mutagens

Radiation- X rays, UV damage

Chemicals- asbestos, formaldehyde

High Temperature

Genotype –the genetic makeup of an organism

Dominant alleles are described using a capital letter. (code for proteins)

Recessive alleles are described using lower case. (do not code for proteins)

Phenotype - the appearance of the trait in an organism

Hybrid, Heterozygous – having 2 different alleles for a trait

Pure, Homozygous - having the same alleles for a trait

Gregor Mendel and the Principles of Inheritance

Gregor Mendel

attended the University of Vienna

Studied math and botany

Was going to be a high school teacher

Became a monk and studied hereditary in pea plants

Laid down the groundwork for further studies in the mechanisms of inheritance

Mendel and the Pea

utilized the pea plant to study the inheritance of traits

readily available

Grew and reproduced quickly

Could self-pollinate or cross-pollinate

Reproduction was controllable

Many observable traits to study e.g. flower colour, pea shape

Pure breeding Plants

Crossing the Parent Generation

Mendel cross-pollinated pure-bred plants that were different for one trait e.g. height

The parent plants made up the parent generation (P generation)

Cross-Pollinating Plants

The stamens which contain pollen is removed from one plant. This is important to prevent self-pollination.

Pollen from another plant is directly applied to purple flower.

It is through this process Mendel controlled reproduction of the pea plants.

Monohybrid Cross

From the experiment Mendel concluded that the trait for tall plants was dominant and the trait for short plants was recessive.

Dominant allele

Expressed when present

Designated with a capital letter

E.g. W is used for widow’s peak

Recessive allele

Only expressed in the absence of a dominant allele

Designated with a lower case letter

E.g. w is used for a continuous hairline

Principle of Dominance

Developed by Mendel

When organisms are crossbred only dominant traits will be expressed

Law of Segregation

Two alleles code for a trait (e.g. Yy)

Each allele comes from one parent’s sex cell that was formed through the process of meiosis

Punnett Squares

When Mendel studied pea plants he initially examined the inheritance of one trait at a time.

This is referred to as a monohybrid cross

To illustrate how traits are inherited Mendel utilized a Punnett square, which is a tool used to show the various combinations of alleles that result when two parents mate.

Let’s explore how a monohybrid cross works by using a Punnett square with an example.

Complete Dominance

Both of the examples that we examined demonstrate complete dominance

Complete dominance means that one allele is always dominant over the other

In our example tall is completely dominant over short

The only way a short pea plant can be produced is if an offspring inherits two recessive alleles

What is a virus?

Non-living

Has genetic material (either DNA or RNA)

Can reproduce quickly

When it reproduces it has to take over another cell in order to do so (can’t reproduce on its own)

Viruses come in different shapes and sizes, but all have general features that are similar to each other. Pictured to the right is a typical bacteriophage, a virus that infects bacteria.

DNA - This is the genetic material for the virus

Capsid - This protein coat protects the DNA.

Tail Fibre - These structures help secure the virus onto it's host ("victim")

Step 1:The virus attaches to the cell

Step 2:The virus' DNA enters the cell.

Step 3:The cell's DNA is destroyed and the cell is forced to make new viral DNA and proteins.

Step 4:New viruses are made inside of the host cell using the DNA and protein in step 3.

Step 5:The cell breaks open and viruses are released.

Lysis - disintegration of a cell by rupture of the cell wall or membrane.

Step 1: The virus attaches to the cell

Step 2: The virus' DNA enters the cell.

Step 3: Viral DNA mixes with the cell's DNA.

Step 4: The cell continues to replicate, copying the viral DNA with it's own.

To exit the lysogenic cycle, some kind of trigger, a chemical, change in temperature or even pH can set off the virus in all the infected cells. At that point the viral infection enters the lytic cycle where we can see the symptoms of the infection.

When viruses infect cells they can sometimes enter into a dormant or "sleep-like" state where we wouldn't see the infection. Although it may seem like the virus isn't doing anything to our bodies, they are slowly replicating.

Kingdom Archaea

Found in extreme-environments

Also called extremophiles

Hot springs, sea-floor vents, alkaline or acidic waters, saline environments

Volcanoes, piles of hot coal, in rocks deep below the Earth’s surface

Obtain energy from inorganic molecules or from light

Methanogens

Methane producing archaea

Live in oxygen-free environments (swamps, marshes, sewage disposal plants)

Use CO2 gas, and H2S as a source of energy

Methane is the waste product

Halophiles

Salt-loving archaea

Live in salt pools (15% salt)

Incorporate pigmentation in the form of bacteriorhodopsin, for photosynthesis, and carotenoids for UV protection.

The caretonoids give them a pinkish color,

To prevent an exodus of water from the cell, halophiles offset the high salt in the environment by accumulating such compounds as potassium and glycine-betaine. This allows a balance of salts inside and outside of the cell preventing water from flowing outward as would be the case if lower salt levels existed within the cells.

Thermoacidophiles

Heat and acid-loving archaea

Live in hot sulfur springs, volcanoes, deep sea vents.

Grow best at temperatures above 80°C

Use sulfur as their source of energy

KINGDOM: EUBACTERIA

Prokaryotes

Most live as single cells

Some live in colonies or link together to form filaments

Can be classified by their shape, cell wall structure, and source of food and energy

Shapes and sizes

Cocci (round)

Bacilli (rod-shaped)

Spirilli (spiral-shaped)

Vibrio (comma-shaped)

Growth pattern

Bacteria often grow in characteristic patterns, or groupings

Diplo- (arranged in pairs)

Staphylo- (arranged in clusters (think: grapes))

Strepto- (arranged in chains)

Cell Wall Structure

Gram stain identifies differences in cell walls such as amino acid and sugar arrangements

Gram Positive: thick protein layer on cell wall and stain PURPLE

Gram Negative: thin protein layer and stain PINK

Asexual Reproduction

Sexual Reproduction

Plasmids

Chromosomes are not the only part of the cell to contain DNA.

Plasmids are small loops of DNA that are separate from the main chromosome.

Plasmids can be transferred from one bacterial cell to another during conjugation.

They are used to introduce foreign genes into bacterial cells.

Spore Formation

The life cycle of some bacteria include a dormant stage.

The bacteria form a tough outer covering that surrounds the DNA and a small portion of cytoplasm—forms endospores.

During this stage, endospores do not grow or reproduce

Used to resist extreme environments.

Bacteria and Health

Bacteria can:

Spoil food

Sour milk

Cause disease

Improve the look of wrinkles

Aid in digestion

Produce necessary vitamins

Clostridium botulinum

Causes botulism, a type of food poisoning

The same toxin produced by C. botulium is used for cosmetic purposes to prevent wrinkles and prevent excessive sweating

Bacteria and Medicine

Antibiotics work to stop bacteria from growing by interfering with specific processes that are essential for growth and reproduction

Kill bacteria
Inhibit bacterial growth

Taxonomy-The branch of biology that considers the classification of organisms.

The hierarchy is domain, kingdom, phylum, class, order, family, genus and species

Species: A group of organisms that resemble one another physically, behaviourally, or genetically, and that can interbreed under natural conditions to produce fertile offspring.

Why Do We Classify Organisms?

To determine a particular organism

To determine evolutionary relationships among organisms.

How Do We Name a Species?

The scientific name of a species consists of two parts:

Genus name

Species name

Canis familiaris– dogs

Example: Homo sapiens - humans

Rules when Writing Scientific Names

The first name is the Genus name → This is capitalized

The second name is the species name → this is NOT capitalized

The entire name must be EITHER typed in italics OR underlined if written by hand

What Exactly Happened?

Membrane-Bound Organelles

Mitochondria = membrane-bound organelle that produces energy for the cell

Mitochondria and chloroplasts are a result of prokaryotes engulfing purple bacteria ( aerobic bacterium) and photosynthetic bacteria(cyanobacterium)

Chloroplast = membrane-bound organelle that captures sunlight and uses it to make food for the cell

Evidence in support of the endosymbiotic theory:

Similarities between mitochondria, chloroplasts, & prokaryotes:

1. Circular DNA and ribosomes

2. Reproduce similarly/binary fission

3. Inner membrane Composition

1. DNA and ribosomes

Chloroplasts and mitochondria both contain their own DNA and ribosomes

The DNA is circular🡪 very similar to ancient prokaryotes

Ribosomes in chloroplasts and mitochondria also have the same structure as ancient prokaryotes (yet the ribosomes in the rest of the eukaryotic cell look different)

2. Reproduction/binary fission

Choloplasts and mitochondria in eukaryotes reproduce EXACTLY the same way as ancient bacteria

3. Inner membrane composition

Cholorplasts and mitochondria have an inner membrane and an outermembrane.

The inner membrane has proteins that do not exists on the outer membrane .

Surely enough these proteins are found on outer membranes of ancient bacteria membranes (supporting the engulfing process)

I Domain Archaea

1. Kingdom Archaebacteria

they are unicellular, prokaryotic
and some are autotrophic and
others heterotrophic

They are different from
bacteria in the structure and
chemical makeup of their cells.

Cell walls of different compositions

known as “ancient bacteria”; they are the most primitive type of organisms

they thrive in the most extreme environments on Earth; they are often referred to as “extremophiles”

found in thermal vents, hot springs, very salty water, swamps, and the intestines of cows

II. Domain Bacteria

2. Kingdom EuBacteria

They are found everywhere on Earth except extreme environments.

They are unicellular, prokaryotic, some are autotrophic and others are heterotrophic.

Cell wall made of peptidoglycan

III. Domain Eukarya (Eukaryota)

Kingdoms:

the “odds and ends” kingdom;

includes any organism that can not be classified as a animal, plant, or fungus

eukaryotic

most are unicellular, others are multicellular

some are autotrophs, others are heterotrophs

Some have a cell wall

Fungi

eukaryotic

most are multicellular (yeast-unicellular)

heterotrophic

include yeast (unicellular), molds, mildews, and mushrooms

Cell wall made of chitin

Plants (Plantae)

multicellular

eukaryotic

autotrophic

most live on land

Cell wall of cellulose

Animals (Animalia)

multicellular

eukaryotic

heterotrophic

live in diverse environments

The Three domains

I. Archeae: very primitive forms of bacteria

II. Bacteria : more advanced forms of bacteria

III. Eukaryota: all life forms with eukaryotic cells

Organisms can be:

Prokaryotic – cells that lack a nucleus

Eukaryotic – cells that contain a nucleus

Unicellular – single-celled; made up of one cell

Multicellular – made up of many cells

Autotrophic – can make their own food

Heterotrophic – can not make their own food

7 Characteristics of Living Things

1…are composed of cells.

Single-cell organisms have everything they need to be self-sufficient.

In multicellular organisms, specialization increases until some cells do only certain things

2…have different levels of organization.

Both molecular and cellular organization.

Living things must be able to organize simple substances into complex ones.

Living things organize cells at several levels:

Tissue - a group of cells that perform a common function.

Organ - a group of tissues that perform a common function.

Organ system - a group of organs that perform a common function.

Organism - any complete living thing.

3. …use energy for maintenance and growth.

4. …respond to their environment.

5. …grow.

6. …reproduce.

7. …adapt to their environment.

Why is it Important to Classify Living Things?

Farmers and gardeners need to be able to identify weeds

Doctors need to be able to identify bacteria

Many groups of peoples, collect plants for medicinal uses—very important to be able to identify the plants.

Classification can assist in:

the discovery of new drugs, hormones, and other medical products

tracing the transmission of disease and the development and testing of possible treatments

increasing crop yields and disease and pest resistance

environmental conservation of organisms

Where Do We Start?

All of the millions of species on Earth share certain fundamental similarities

Species do exhibit structural diversity—diversity that is based on external and internal structural forms—that allow us to organize and identify.

Species can be classified by:

Biological Species Concept

Morphological Species Concept

Phylogenetic Species Concept

Prokaryotic Cell: most ancient cell type; no membrane bound nucleus (i.e. bacteria); unicellular

Eukaryotic Cell: Has a ‘true nucleus’ and is membrane bound; multicellular