What is a niche?A niche is the is the role played by an organism in an ecosystem. Eg: The ecological niche of a trees in a yard is absorbing light, water and nutrients, providing shelter and food for other organisms (birds, squirrels, bees), and giving off oxygen.

What is adaptation?

Adaptation is the modifications or

changes made to the body of an organism to

make it suited to survive in a changing

environment.What is natural

selection?Natural selection is an event that favours the organisms which have managed to adapt and

survive.

What is a gene pool?The gene pool is the set of all genes, or genetic information, in any population,

usually of a particular species.

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Natural Selection1. There is variation in traits.For example, some beetles are green and some are brown.2.There is differential reproduction.

Since the environment can't support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do.3. There is heredity.

The surviving brown beetles have brown baby beetles because this trait has a genetic basis

4. End result:The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. If this process continues, eventually, all individuals in the population will be brown.

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• Biodiversity is measured by the frequency of an allele in a particular frequency .

• The bigger the gene pool of a certain population , the lesser the chances of a gene getting removed from the population increasing biodiversity .

• If the change in genetic information is positive and helps the organism survive , the frequency with the changed gene will increase.

• If the change is negative , natural selection will result in its removal from the gene pool.

• Rarely the change is neutral which means that there is no positive or negative effect of the change then the gene will remain in the gene pool.

The founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population  The original

population has nearly equal numbers of blue

and red individuals. The three smaller

founder populations show that one or the

other color may predominate (founder effect), due to random

sampling of the original population.

A population bottleneck may also

cause a founder effect even though it is not

strictly a new population.

Any founder member of new populations might become amplified over the next generations as the population increases.

Darwin made two observations and a conclusion;O1: More offsprings are born than can surviveO2: There is variation within a species

Conclusion: There is a “struggle for survival” only the “fittest cansurvive and reproduce.”In order for Natural Selection to lead to evolution a few extra conditions are required;

Ecological

TemporalBehavior

alMechani

calThe species occupy different parts of the habitats.

The species exist in the same area but reproduce at different times.The species exist in the same area but do not respond to each other’s courtship behavior.Species coexist, but there are physical reasons which stop them from copulating.

Isolation

1. Isolation2. Mutation3. Mutations accumulate within population4. Eventually the isolated population cannot reproduce with the originals. At

this point a new species has formed. (speciation)

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Phenotype Frequency over time

Directional Selection occurs where environmental pressure exists, cause them to modify themselves and adapt to the changing environment.

Directional selection

Directional selection is a type of natural selection that favors one extreme phenotype over the mean or other extreme phenotypic. 

When selective pressures select against the two extremes of a trait, the population experiences stabilizing selection.

Disadvantage - Variation waves off. Includes ruling out of beneficial extreme phenotypes.

Advantage – Continuous inheritance of beneficial genes.

Balancing Selection

Phenotype Frequency over time

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In disruptive selection, selection pressures act against individuals in the middle of the trait distribution. The result is a bimodal, or a two-peaked curve.This occurs when conditions of the organism’s surroundings are very diverse and the organisms evolve according to the surrounding or condition chosen.

Diversifying Selection

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Selective Breeding is the breeding of only those organisms with desirable features. It is also referred to as artificial selection.

Liger is a hybrid cross between a male lion (Panthera leo) and a tigress (Panthera tigris).

Loganberry, a hybrid between raspberry and black berry.

ZebroidsA zebra-horse cross.

Selective Breeding & Hybridization

This is in contrast to natural selection as in selective breeding, humans provide the selection pressure rather than the environment.

Hybridization is the cross match between two different breeds. This cross breeding results in an organism inheriting genes from both the species.