Natural selection and speciation

Question 1

Genetic and environmental factors cause ….

Answer 1

Variation

Question 2

What is the primary source of genetic variation?

Answer 2

Mutation

Question 3

Define gene pool

Answer 3

All of the alleles of all of the genes of all the individuals within a particular population at a given time

Question 4

What is intraspecific competition?

Answer 4

Competition between individuals of the same species

Question 5

Give 3 reasons why differential survival and reproduction could occur.

Answer 5

Predation

Disease

Competition

Question 6

An organism has a selecive advantage. What does this mean?

Answer 6

Better adapted for the conditions present.

More likely to survive and reproduce.

Pass on favourable alleles

Question 7

How is genetic variation produced?

Answer 7

Crossing over

Independent segregation/random assortment

Random fusion of gametes

Mutation

Question 8

Name 3 types of selection

Answer 8

Stabilising

Directional

Disruptive

Question 9

Describe stabilising selection

Answer 9

Preserves the average phenotype

Selection against extreme phenotypes.

Occurs when environment is stable

Question 10

Give an example of stabilising selection

Answer 10

Human birth weight

Question 11

Give an example of directional selection

Answer 11

Antibiotic resistance in bacteria

Question 12

Give a defition of speciation

Answer 12

Evolution of a new species from an existing one

Question 13

Define a species

Answer 13

Group of similar organisms that breed producing fertile offspring

Question 14

Give the 2 types of speciation

Answer 14

Allopatric and sympatric

Question 15

Allopatric speciation occurs when …..

Answer 15

When 2 populations become geographically isolated

Question 16

Give examples of how organisms might be geographical isolated

Answer 16

Physical barrier which prevents interbreeding e.g. oceans, rivers, mountains, deserts, landslide

Question 17

Define reproductive separation

Answer 17

when 2 populations can no longer interbreed and produce fertile offspring

Question 18

Example of allopatric speciation

Answer 18

Finches on the Galapagos Islands!

Question 19

Sympatric speciation occurs

Answer 19

Within a population of organisms living in the same area (doesn’t require geographical isolation)

Question 20

Sympatric speciation arises because ….

Answer 20

They have different breeding seasons
They may inhabit different habitats in the same area so never meet, Anatomical differences,

Question 21

Name the type of selection shown

Answer 21

stabilising

Question 22

Name the type of selection shown

Answer 22

directional

Question 23

Describe how allopatric speciation occurs

Answer 23

Two populations are geographically isolated

Creates separate gene pools with no interbreeding

Variation due to mutation

Different selection pressures

Differential reproductive success

Leeds to change in allele frequencies

Occurs over long period of time

Populations no longer able to interbreed to produce fertile offspring

Question 24

Name the type of selection shown

Answer 24

Disruptive

Question 25

What does evolution do to the frequency of alleles in a population?

Answer 25

Changes them - increase or decrease

Question 26

What happens to the frequency of the alleles that give organisms an advantage?

Answer 26

Increases

Question 27

What happens to those organisms that are better adapted to the selective pressures in the environment?

Answer 27

Survive, reproduce and pass on favourable alleles

Question 28

What happens to the phenotype during stabilising selection?

Answer 28

Preserves the middle of the range phenotypes

Question 29

Which phenotype is selected for during directional selection?

Answer 29

An extreme phenotype - these are more likely to survive and reproduce

Question 30

What phenotype is preferred in disruptive selection?

Answer 30

BOTH extremes (select against the middle phenotype)

Question 31

What is genetic drift?

Answer 31

Chance (not the environment) determines which organisms survive, reproduce and pass on their alleles

Question 32

Genetic drift has a greater effect on which size population?

Answer 32

Smaller populations

Question 33

Describe Sympatric Speciation

Answer 33

Occurs in the same population Mutations cause variation in alleles Reproductive separation with no gene flow Different alleles selected for Change in allele frequency Disruptive selection Different species formed which cannot interbreed