por Danielle Coffey hace 11 años
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Causes: -Temperature decrease -Darker -photosynthesis decrease -productivity decrease (worldwide)
Causing:
Biological Changes: -Lattitudinal/poleward shift in species ranges -earlier spring events/later fall events -coral bleaching -species extinctions
Most Negatively Effected: -cold adapted organisms -severely range restricted species
ex) Maple tree ranges moving North Beech tree ranges moving north Euphydaas editha (butterfly) moving north along west coast
Physical Environment Changes: -warmer ocean temperatures (releases methane gas) -Higher sea levels (due to glacier melting) -more intense hurricanes -change in percipitation
retardation of heat escaping the atmosphere by certain "greenhouse gases"
Ozone Depletion (Concentration thinning)
greatest depletion of ozone over SOUTH POLE (ANTARTICA)
allows UV light to more easily penetrate Earth's surface
have seen in increase in skin cancer
Positive correlation to temperature RISE
CO2 "Sinks" -photosynthetic plants -oceans
Bipedalism was more beneficial seeing as the African Rift Valley was changing from a tropical to a savannah landscape. Standing upright allowed our ancestors to see above the tall grasses, reach food on trees, cool more efficiently from the sun, and most notably: conserve more energy (as this was more energy efficient than walking long distances on four legs).
Australopithecus over 4mya
Extinctions caused by ENVIRONMENTAL CHANGES.
A. ganhi
Homo erectus 1.8mya-350,000 moved out of Africa to Middle East, Asia...
Adaptations such as endurance running, sweating, and less body hair were seen here.
lead to "Persistence Hunting" (needed bigger meaty foods to support larger bodies and brains).
(Archaic) Homo sapiens evolved 350,000 years ago
H. sapiens sapiens (move from Africa and Middle East)
H. sapiens sapiens have ~3% neandertal DNA in us.
Outlived neandertals due to taller slimmer bodies which require less energy to sustain, more advanced hunting tools (such as throwing spears) allowed them to get food without putting themselves in harm's way.
No major extinctions in Africa (people were already residing there from the beginning, thus there was no major change)
Traveled to Asia and Australia 60,000 years ago
Reached South Pacific Islands moving from SE Asia
islands that are much closer geographically have residents that are closer related genetically as well, when compared to islands that are further apart
Traveled to New World 25,000 years ago
North America: extinction of many animals 14,000-6,000 years ago bc hunted to extinction
Presence of humans increases the probability of extinction for animals in the area. Major BIODIVERSITY effect!
Why so little genetic variation today? Theorized bottleneck effect. All mankind today derived from ~600 breeding individuals
Later reached South Americas
H. sapiens neandertals (goes to Europe and Middle East)
FoxP2 gene found in neandertal DNA led scientists to believe neandertals could has possibly had a language.
DIES OUT
Possible causes of extinction:
-Not advanced enough technology to catch food in order to sustain and maintain food requirements for large bodies.
-Lived in cold climates
-H. sapiens sapiens were better adapted to enviornment, started out competeing neandertals, leading to their demise.
Homo habilis 2-1.8mya
First signs of greater encephalization: (more intelligent beings had more offspring- thus, larger brains continued to be passed down)
A. Afarensis (Lucy) common ancestor
development of different PHENOTYPES from a common ancestor due to adaptations to different environments
selection working in opposite directions. There is compeition at the mean so phenotypes diverge in order to reduce competition.
ex) Galapagos Finches Beak Size: separately they are similar, over time beak size diverged to reduce competition in eating the same food.
**also: Competitive Exclusion
sampling error= chance variation from the expected value. With a larger population size, there is less of a chance of sampling error.
Founder Effect
(*Within the same generation)
New "colonizing" population's gene frequencies not likely to be the same as original population due to sampling error.
Bottleneck Effect
After a catastrophe where populations are greatly reduced in size, more prone to extinction bc LOSS OF HETEROZYGOSITY. Could lose an allele which would reduce the amount of genetic variation.
Fixed: allele goes to 1 Lost: allele goes to 0
Most populations either fix or lose an allele by CHANCE, this results in a genetic drift over time.
-Nonrandom mating -Small population size -Mutations must occur -Migration -Sexual selection
sexual selection is ALWAYS phenotypic
-Need random mating -No mutations -Large population size -No migration -No selection
produces deficient (ex. monosomic) or duplicate (ex. trisomic) gametes
Chromatid Disjunciton during Anaphase II
Chromosome disjunction during Anaphase I
