Zo 6.5

Natural Selection


Natural Selection

?        ______________________________________________________________________________

?        Explains the origins of _________________________________, including all developmental, behavioral, anatomical, and physiological attributes that enhance an organism’s ability to use environmental resources to _______________________ and to __________________________.

?        Darwin developed his theory of natural selection as a series of 5 __________________________ and 3 ____________________________________ drawn from them.

Observation 1

?        ______________________________________________________________________________


?        All populations produce large numbers of _________________________ and potentially large numbers of _______________________________ each generation.  Population size would increase _______________________________________ at an enormous rate if all individuals that were produced at each generation survived and reproduced.

?        Darwin calculated that, even in slow-breeding animals such as elephants, a single pair breeding from age 30-90 and having only 6 young could produce ___________________ descendents in 750 years.

Observation 2

?        _________________________________________________________________________


?        Natural populations _______________________________ in size across generations and sometimes go extinct, but no natural populations show the continued ____________________________________________ that their reproductive biology theoretically could sustain.

Observation 3

?        ______________________________________________________________________________

?        Exponential growth of a natural population would require ________________________

_________________________________________________ to provide food and habitat for the expanding population, but natural resources are finite.

Inference 1

?        A continuing _____________________________________________ exists among members of a population.

?        Survivors represent only a part, usually a ________________________________, of the individuals produced each generation.

?        Darwin wrote in On The Origin of Species that “it is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms.”

?        The struggle for food, shelter, and space becomes increasingly severe as _______________________________________ develops.

Observation 4

?        ___________________________________________________________________________


?        No 2 individuals are exactly alike.

?        They differ in:

?        _____________________________

?        _____________________________

?        _____________________________

?        _____________________________

?        Etc.

Observation 5

?        ______________________________________________________________________________

?        Darwin noted that offspring tend to ______________________________________ their parents, although he did not understand how.

?        The hereditary mechanism discovered by ______________________________________ would be applied to Darwin’s theory many years later.

Inference 2

?        Varying organisms show ___________________________________________________ favoring advantageous traits.

?        Survival in the struggle for existence is _________________________________ with respect to hereditary variation present in the population.

?        Some traits give their possessors an _________________________________ in using the environment for effective survival and reproduction. 

?        Survivors ________________________ their favored traits to accumulate in the population.


Inference 3

?        Over many generations, __________________________________________________________


?        The _____________________________________ reproduction of varying organisms gradually transforms species and results in their long-term “improvement.”

?        Darwin knew that people often use _________________________________ variation to produce useful new breeds of livestock and plants.

?        _____________________________________ selection acting over millions of years should be even more effective in producing new types than _______________________ selection imposed during a human lifetime.

?        ____________________________________________ acting independently on geographically isolated populations would cause them to diverge from each other, thereby generating ________________________________________________________ that lead to ________________________________________________.