Cycles
Reproduction
Reproduction in plants
There are male and female parts in a flower.
The female part contains an ovary and stigma.Inside the ovary are ovule with eggs(ovum).
The male anther produces reproductive cells called pollen grains .The function of pollen grains is to fertilise eggs inside the ovules.
Some flowers have male and female parts in separate flowers.They are called uni-sexual flowers
examples-maize,cucumber,papaya,etc.
Some plants have male and female parts in the same flowers.They called bi-sexual flowers
examples-hibiscus,morning glory,etc.
Plants reproduce to ensure the survival of their kind.
Dispersal of seeds
Animals/insects
Some of these fruits and seeds have small hard,indigestible seeds that are passed out in the animals' dropping
Some seeds have hooks to hook onto the fur ,feathers and hair of passing animals
Some fruits are fleshy and juicy. Animals are most likely to eat only the flesh and throw the seeds further away from the parent plant.
Wind
Some fruit and seeds have hairs and wing-like structures to enable them to float longer in air.
Other seeds with no special structures are minute and light
Water
Fruits and seeds are covered with a thick layer of fibrous husk that traps air and enables them to float.
Explosive action
These fruits split open when they are dry.They scatter their seeds further away from the parents plant.
Methods of reproduction-Reproduce through seed,reproduce through spores,reproduce by vegetative propagation
Sexual reproduction
While living things reproduce, their characteristics are passed down to their young too. examples-colour of skin,height,attached/detached earlobe,ability to roll tongue,etc.
Sexual reproduction involves a female reproduction cell and a male reproduction cell.The process the male reproduction cell(sperm) fuses with the female reproduction cell(egg/egg cell) is known as fertilization.
When fertilisation takes place internally.(While the fertilised egg is still in the mother's body), most of these animals usually give birth to their young. examples-mammals (human beings, kangaroo,koala,dolphin,etc.
The period from fertilisation to birth is known as gestation period.During this period, ,fertilised egg goes through changes within the mother's body before it become a young animal that is ready to born.This period usually takes nine month for human beings.
When fertilisation takes place externally,(after the egg is laid), most of these animals usually lay eggs which later hatch into young.Eggs that are laid unfertlilised will not hatch into young. examples-reptile,fish,insect,bird,amphibian
Cycles in matter and water
Freezing
When the temperature of the water falls to 0 degrees Celsius, liquid water changes into ice.This process is called freezing.
The temperature at which a liquid freezes is called its freezing point.The freezing point of pure water is 0 degrees Celsius.
Freezing point is a heat loss process.Waters needs to lose heat and cooled down to 0 degrees Celsius.
Melting
At 0 degrees Celsius,Ice melts and changes back into water. This process is called melting
The temperature at which a solid change into a liquid is called melting point .The melting point of ice is 0 degrees Celsius
For melting to take place, a solid needs to gain heat energy.
Solids lose their shapes when they melt into liquids as liquids have no definite shape.
Boiling
At 100 degrees Celsius, water changes from liquid to gas.This process known as boiling.
The boiling point of pure water is 100 degrees Celsius
Under normal conditions, the highest temperature that pure water can reach is 100 degrees Celsius.Any additional heat gained by the water after that is used to convert inti its gaseous state (steam).
Evaporation
Evaporation is a process by which a liquid changes into a gas.For example, a drop of water that has spilled on a desk will "disappear" and turn into water vapor after some time due to evaporation
Evaporation takes place all the time and at any temperature
During evaporation, a liquid gains heat from surrounding
Condensation
When water vapor and steam are cooled down, they change from gaseous state to liquid state.
Water vapor condenses in to liquid whenever it touches a surface that is cooler in temperature.