3.7.3 Evolution may lead to speciation

Question 1

What do you call the environmental factors that limit the population of a species?

Answer 1

selection pressures e.g. predation, disease, competition

Question 2

Define gene pool

Answer 2

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

Question 3

All populations have the potential to increase exponentially - why in nature is this rarely the case

Answer 3

death rates must be high which is compensated for by the high reproductive rates. Some species have lower reproductive rates but have higher degree of parental care , the lower death rate from this maintains their population size.`

Question 4

What is the consequence of over-production?

Answer 4

competition between individuals - intraspecific

Question 5

What determines which individuals survive in over production?

Answer 5

The best adapted organisms to the conditions at the time survive and reproduce and pass on favourable allele combinations.

Question 6

Why do organisms NOT produce organisms identical to itself when it survives the condition it lives in?

Answer 6

Meiosis - offspring produce show variation from the parent, this may may result in offspring more or less likely to survive. Environment changes all the time, this way there is an wide range of genetically different organisms in the population.

Question 7

Consequences of populations showing little genetic diversity

Answer 7

more vulnerable to disease and climate changes.

Question 8

A larger population showing greater genetic diversity means

Answer 8

There is a greater chance that one or more individuals will have the correct combination of alleles for survival

Question 9

Individuals that survive the struggle for survival can

Answer 9

more likely to breed/reproduce, pass on favourable allele combinations to future generations.

Question 10

Name 3 types of selection

Answer 10

stabilising, directional and disruptive

Question 11

Describe stabilising

Answer 11

preserves the average phenotype, selection against extreme phenotypes. Environment pretty stable

Question 12

Describe directional

Answer 12

Phenotype of population changes, favouring phenotype at one direction from the mean (selection for one extreme phenotype). Environmental conditions change.

Question 13

Describe disruptive

Answer 13

Preserves individuals with extreme phenotypes (both ends), not those around the mean. Opposite to stabilising. Least common selection. Environment changes taking 2 distinct forms

Question 14

which types of selection is being described: A baby born with a birth weight of more than 4kg and less than 2.5kg has a greater risk of dying

Answer 14

stabilising

Question 15

Elephants have evolved longer trunks enabling them to reach leaves higher up in the trees

Answer 15

directional

Question 16

small mammals can escape from predators by hiding in small places while large mammals can resist attack from predators

Answer 16

disruptive

Question 17

the most important selection in bringing about evolutionary change

Answer 17

disruptive

Question 18

define speciation

Answer 18

the evolution of a new species from an existing one

Question 19

define a species

Answer 19

group of similar organisms that are capable of breeding and producing fertile offspring - they share a common ancestry (same genes different alleles)

Question 20

summarise how a new species is formed

Answer 20

because of reproductive separation, variation followed by natural selection

Question 21

define adaptive radiation and consequences of this

Answer 21

when each population becomes adapted to its local environment, leading to changes in allele frequency in the population

Question 22

identify 2 forms of speciation

Answer 22

allopatric and sympatric

Question 23

the genetic diversity of a small population can be described as

Answer 23

Less - as there is a smaller variety of alleles in a small populations

Question 24

the genetic diversity of a large population can be described as

Answer 24

Great - as there is a larger variety of alleles in a large populations

Question 25

The effect of genetic drift is greater on which population size - small or large?

Answer 25

small

Question 26

Allopatric means

Answer 26

different countries

Question 27

Allopatric speciation means

Answer 27

When 2 populations become geographically isolated

Question 28

Examples of geographical isolation…

Answer 28

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

Question 29

Define reproductive separation

Answer 29

when 2 populations can no longer interbreed and produce fertile offspring

Question 30

Example of allopatric speciation

Answer 30

Finches on the Galapagos Islands!

Question 31

Sympatric means

Answer 31

same country

Question 32

Sympatric speciation occurs

Answer 32

within a population of organisms living in the same area (doesnt require geographical isolation)

Question 33

sympatric speciation arises because

Answer 33

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

Question 34

Name the type of selection shown

Answer 34

stabilising

Question 35

name the type of selection shown

Answer 35

directional

Question 36

name the type of selection shown

Answer 36

disruptive

Question 37

main source of variation within the same species

Answer 37

mutation (creating different alleles)

Question 38

mutations in DNA creates

Answer 38

new alleles - new characteristics

Question 39

Variation between species is also brought about during

Answer 39

meiosis

Question 40

variation is also brought about between members of the same species because of the …

Answer 40

environment

Question 41

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

Answer 41

changes them - increase or decrease

Question 42

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

Answer 42

increases

Question 43

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

Answer 43

survive, reproduce and pass on favourable alleles

Question 44

What happens to the environment in stabilising selection?

Answer 44

it doesnt change

Question 45

What happens to the phenotype during stabilising selection?

Answer 45

preserves the middle of the range phenotypes

Question 46

Which phenotype is selected for during directional selection?

Answer 46

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

Question 47

What phenotype is preferred in disruptive selection?

Answer 47

BOTH extremes (select against the middle phenotype)

Question 48

In disruptive selection what does the environment select for?

Answer 48

more than 1 phenotype

Question 49

Reproductive isolation can occur in many ways - name them?

Answer 49

seasonal

mechanical

behavioural

Question 50

Genetic drift can lead to ..

Answer 50

speciation

Question 51

What does selective pressures do to allele frequencies?

Answer 51

changes them!

Question 52

What is genetic drfit?

Answer 52

This is when chance (not the environment) determines which organisms survive, reproduce and pass on their alleles

Question 53

Genetic drift has a greater effect on which size population?

Answer 53

smaller populations

Question 54

Genetic drift has less of an effect on which sized population?

Answer 54

larger populations