9B Selection pressures

Question 1

Evolution

Answer 1

The continual process of change in species of living things

Question 2

Natural selection

Answer 2

The differential survival and reproduction of individuals in a species based on heritable differences in their phenotypes.

Question 3

Acquired characteristics

Answer 3

An acquired characteristic is one that an individual develops during it’s lifetime

Question 4

Genotypic variation

Answer 4

The genetic differences between individuals

Question 5

Phenotypic variation

Answer 5

The physical, structural, physiological or behavioral differences between individuals

Question 6

Darwin’s observation #1

Answer 6

There is phenotypic variation within species

In any species of any population the physical characteristics
( phenotypes ) have variation.

Question 7

Darwin’s observation #2

Answer 7

Offspring tend to inherit the traits of their parents

The offspring inherits phenotypic traits that the parents have e.g., hair colour and height.

Question 8

Darwin’s observation #3

Answer 8

Species produce more offspring than required to replace themselves

Most species have more offspring than what would replace the parents. e.g., turtles producing average of 80 eggs / nest when they only need 2.

Question 9

Darwin’s observation #4

Answer 9

There is a struggle to survive

Some animals don’t hatch or are eaten by other animals. For example sea turtles are often eaten by sea birds before they make it to sea

Question 10

Selection pressure

Answer 10

The environmental factor which causes differential death in members of a species due to their phenotypic variation

Question 11

Selecting agent

Answer 11

The element of the environment that exerts a selection pressure.

Question 12

Fitness

Answer 12

The relative chance that an individual will contrivute to the gene pool of the next generation

Question 12

Selective advantage

Answer 12

a synonym for fitness

Question 13

Darwin’s first inference

Answer 13

1. Individuals whose traits give them more chance to survive and reproduce leave more offspring than other individuals.

Question 14

Allele frequency

Answer 14

The fraction ( or percentage ) of chromosomes in a population that carry a specific allele

Question 15

Darwin’s second inference

Answer 15

2. The unequal chance of reproduction will lead to accumulation of favorable traits in the population over generations.

Question 15

Sexual selection

Answer 15

A form of natural selection in which the selection pressure is the ability to obtain a mate

Question 16

Female choice

Question 17

Tournament species

Answer 17

One sex ( usually males ) fight with each other for the right to mate with all the females

Question 18

Explain why natural selection reduces genetic diversity.

Answer 18

Natural selection reduces the genetic diversity of a population as it is reducing the ‘ unfit ‘ phenotypes leaving less diversity. This is the opposite of mutations which increase the diversity.

Question 19

Explain why natural selection is often stabilising.

Answer 19

Natural selection is often stabilising meaning that natural selection removes the unfit phenotypes and narrows It down so they are mostly the same.

Question 20

Explain what causes directional selection

Answer 20

change in the environment e.g. new predator/ disease / temperature, selection pressure may change. suddenly advantage for uncommon phenotype. Natural selection eliminates all the disadvantaged species.

Question 20

What increases genetic mutation?

Answer 20

Genetic mutation is increased by creating new alleles increases the genetic diversity

Question 21

What decreases genetic mutation?

Answer 21

natural selection decreases as it selects against certain mutations that are unfavourable