Populations Natural Selection And Evolution Essay Research - Реферат

Populations, Natural Selection And Evolution Essay, Research Paper

Outline

how population size can be affected by natality, immigration, mortality and

emigration. Natality = + Immigration = + Mortality = – Emigration = – Draw

a graph showing the sigmoid shaped population curve. ? Explain

reasons for the exponential growth phase, the plateau phase and the

transitional phase between these two phases.

Lag Phase o

Only a few individuals to breed

Exponential Growth Phase o

Numbers increase. More individuals are available for

reproduction. o

Population grows at an every increasing rate, with no

inhibitors

Plateau Phase o

There is a limit to the number of individuals that a

community can support. o

The population has reached its environment?s carrying

capacity. o

Factors limit population growth

Death Phase o

The high population causes carrying capacity to

decline. o

Pollution builds up. Population rapidly declines.? Define

carrying capacity. The maximum number of a species that can be sustainably

supported by the environment. List

three factors which set limits to population increase

Pollution

Amount of food available

Predators State

that population trends tend to produce more offspring than the environment can

support Explain

that the consequences of the potential overproduction of offspring is a

struggle for survival

Overpopulation

Scarce resources

Survival of the fittest State

that the members of a species show variation Explain

how, by natural selection, the best adapted will survive to breed.

Natural

selection keeps the disorganizing effects of mutation and other processes in

check because it multiplies beneficial mutations and eliminates harmful ones.

Natural

selection may occur not only because of competition but also because of some

aspect of the physical environment, such as inclement weather. Moreover,

natural selection would occur even if all the members of a population died at

the same age, simply because some of them would have produced more offspring

than others. Discuss

the theory that species evolve by natural selection Natural selection can be defined as the differential

reproduction of alternative hereditary variants, determined by the fact that

some variants increase the likelihood that the organisms having them will

survive and reproduce more successfully than will organisms carrying alternative

variants. Natural selection is quantified by a measure called Darwinian

fitness, or relative fitness. Fitness in this sense is the relative probability

that a hereditary characteristic will be reproduced; that is, the degree of

fitness is a measure of the reproductive efficiency of the characteristic. Evidence

Fossil Record

Structural Similarities

Embryonic Development

Molecular Biology Discuss

the need for evolution in response to environmental change

Darwin

maintained that competition for limited resources results in the survival of

the most effective competitors.

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