Unit ____: Natural Selection                          Name: _____________________________

Natural selection increases the frequency of characteristics that make individuals better adapted.  This leads to changes within the species (5.1.U1 and 5.2.U7).

• Define evolution, natural selection and fitness.
• State that selection acts on individuals resulting in evolution of the population.
• Compare the reproductive success of better and less well-adapted individuals in a population.

Species tend to produce more offspring than the environment can support (5.2.U4).

• State that species have the ability to produce more offspring than the environment can support.
• Use an example to illustrate the potential for overproduction of offspring in a population.
• Define carrying capacity.
• Compare exponential and logistic models of population growth.

Natural Selection can only occur if there is variation among members of the same species (5.2.U1, 5.2.U2 and 10.2.U3).

• Define variation.
• Outline the role of genes and environment on phenotype.
• Explain why natural selection can only function if there is variation in a species.
• State that only inherited variation can be acted upon by natural selection.
• Outline sources of genetic variation (mutation, meiosis and sexual reproduction).
• Contrast discrete with continuous variation.
• State an example of a discrete variation.
• State an example of a continuous variation.

Selective pressures influence the survival and reproduction of individuals in a population.

• Define selective pressure.
• State example selective pressures.
• Outline how a selective pressure acts on the variation in a population.

Individuals that are better adapted tend to survive and reproduce, passing on the favorable adaptation to their offspring while those who are less well-adapted tend to produce fewer or no offspring (5.2.U3, 5.2.U5 and 5.2.U6).

• Explain the effect of the selective pressure on the more and less adapted individuals in a population.
• Define adaptation.
• List examples of adaptations.

Evolution is the change in the heritable characteristics of a population over successive generations.

• Explain the cause of the change in frequency of heritable traits in a population through natural selection.
• Outline the effect of the strength of a selective pressure on the rate of change in the population.

Natural selection can change the frequency of individuals with particular traits, depending which phenotype is more favorable within a particular environment (10.3.A1).  

• Define stabilizing, disruptive and directional selection.
• Use graphs to illustrate or identify stabilizing, disruptive and directional selection.
• Outline an example of stabilizing, disruptive and directional selection.

Evolution

Definition:

Natural Selection

• Definition:

• “Survival of the Fittest”

  POTENTIAL OVERPRODUCTION OF OFFSPRING

  Genetic Variation in the Population

• occurs when individuals within a population differ in their characteristics.

• may be shown in physical appearance, metabolism or behaviour.

Discrete and Continuous Variation

Sources of Genetic Variation:  Mutation

Sources of Genetic Variation:  Meiosis

Sources of Genetic Variation:  Sexual Reproduction

Sources of Genetic Variation:  Gene Flow

Define:  

Examples:  

• Resource availability:  
• Environmental conditions:  
• Biological factors:  

Adaptations

How does the strength of selection affect the rate at which populations change?

Modes of Natural Selection

Stabilizing Selection

Directional Selection

Disruptive Selection