7.3 Speciation

Question 1

How is variation an advantage?

Answer 1

pops with low variation are not able to withstand change in environments = less likely to have an individual with a phenotype suited for the new environment

Question 2

What are the 2 types of variation?

Answer 2

discontinuous and continuous

Question 3

What is discontinuous variation?

Answer 3

distinct groups = no overlapp
involves features that have distinct categories, with no individuals in between

Question 4

What is continuous variation?

Answer 4

a range of characteristics that change gradually

Question 5

How are phenotypes measured in continuous and discontinuous variation?

Answer 5

discontinuous = qualitative phenotypes
continuous = quantitative phenotypes

Question 6

How many genes is each type of variation controlled by?

Answer 6

discontinuous = 1/2 genes with multiple alleles
continuous = polygenic - controlled by many genes

Question 7

What effect does the environment have on discontinuous variation?

Answer 7

little effect from environment on gene expression

Question 8

What effect does the environment have on continuous variation?

Answer 8

more significant effect from the environment on gene expression

Question 9

What is an example of discontinuous variation?

Answer 9

blood groups in humans - A B O

Question 10

What is an example of continuous variation?

Answer 10

heights, body weight

Question 11

What are the main 2 sources of variation?

Answer 11

genetics and environment

Question 12

What are the 2 genetic causes of variation?

Answer 12

mutations and meiosis

Question 13

How does meiosis cause variation?

Answer 13

crossing over
sexual recombination
random assortment
random fertilisation

Question 14

How does the environment cause variation?

Answer 14

can change a phenotype over time due to changed lifestyles

Question 15

What is the process of natural selection?

Answer 15

1. new alleles for a gene are created by random mutations
2. genetic variation rises in pop
3. if environment changes = leads to competition/predation/ disease
4. if the new allele increases the chances of survival in that environment more likely to survive and reproduce
5. reproduction passes on the advantageous allele
6. over many generations the new allele increases in freq in the gene pool

Question 16

What is evolution?

Answer 16

the change of the allele frequencies in a population over time

Question 17

Why does Hardy-Weinburg disagree with evolution?

Answer 17

the allele freq are constant

Question 18

What is selection pressure?

Answer 18

any environmental pressure that limits the population or kills individuals, results in differential survival and reproduction

Question 19

What is differential survival and reproduction?

Answer 19

some individuals are more likely to survive and reproduce at the expense of others

Question 20

What is an example of a selection pressure?

Answer 20

antibiotics use in the development of antibiotic resistance in bacteria

Question 21

What is disruptive selection?

Answer 21

favours either of the extreme phenotypes

Question 22

What is speciation?

Answer 22

the evolution of new species from exisiting ones

Question 23

What is the process of speciation?

Answer 23

1. pops are reproductively isolated
2. no gene flow between isolated groups - they cannot interbreed
3. different mutations occur in DNA of each group
4. because they are exposed to diff environments
5. subject to diff selection pressures
6. natural selection = diff gene pools of each group
7. diff genetics expressed as diff phenotypes
8. no longer interbreed to form fertile offspring = diff species

Question 24

What is genetic drift?

Answer 24

no selective pressures
there is no favoured phenotype in the pop and only a few individuals can survive the change in the environment

Question 25

What can be said about individuals who have survived genetic drift?

Answer 25

each individual represents a large proportion of the pop in a small pop as not many individuals will survive the change in environment

Question 26

What are the 2 types of genetic drift?

Answer 26

the bottle neck effect and the founder effect

Question 27

What type of population does the bottle neck effect occur in?

Answer 27

very genetically diverse populations

Question 28

What is the bottleneck effect?

Answer 28

a type of genetic drift that occurs when a population's size is severely reduced, often by a natural disaster reducing the genetic diversity of a pop

Question 29

How is the bottleneck population diff to the original pop?

Answer 29

small pop with a random group of survivors they will have a diff allele freq to the original pop and some alleles may be missing entirely reduced genetic diversity of new pop

Question 30

What effect does reducing genetic diverity have on the bottleneck pop?

Answer 30

reduced genetic diversity = makes it difficult for pop to adapt to new selection pressures they are more vulnerable to environment changes

Question 31

Why is a less genetically diverse pop more vulnerable to environment changes?

Answer 31

they are less likely to have alleles that are advantageous to the new envrionment

Question 32

What is the founder effect?

Answer 32

a type of genetic drift that occurs when a small group of individuals break away from a larger population to establish a new colony

Question 33

What effects does the founder effect have?

Answer 33

genotypic and phenotypic differences to original pop inherited diseases speciation

Question 34

What is the difference between the bottleneck effect and the founder effect?

Answer 34

bottleneck occurs when most of the pop is destroyed founder = small group breaks away

Question 35

What are the 3 main causes for differential survival and reproduction?

Answer 35

predation disease competition

Question 36

What is differential reproductive success?

Answer 36

not all individuals are as likely to reproduce and this results in change in allele frequencies within a gene pool

Question 37

How does disruptive selection lead to speciation?

Answer 37

either extreme train is selected for = more likely to survive and pass on genes the allele freq changes and more individuals possess the allele for the extreme train and the average trait becomes less frequent continued disruptive selection leads to speciation

Question 38

What does reproductively isolated mean?

Answer 38

there are 2 populations of the same species but they cannot interbreed together

Question 39

What is allopatric speciation?

Answer 39

populations become separated geographically leading to reproductive isolation

Question 40

What is sympatric speciation?

Answer 40

a population of species is reproductively isolated without geographical separation

Question 41

What is are 2 examples of sympatric speciation?

Answer 41

random mutation may cause individuals to perform a different courtship ritual individuals become fertile at different times of the year

Question 42

What are the 4 ways species can change due to sympatric isolation?

Answer 42

mechanical behavioural ecological temporal

Question 43

How do pops change mechanically due to sympatric isolation?

Answer 43

gametes are no longer compatible changes in reproductive organs = anatomical changes

Question 44

How do pops behaviours change due to sympatric isolation?

Answer 44

a random mutation can cause changes in mating behaviours like courtship rituals

Question 45

How do pops change ecologically due to sympatric isolation?

Answer 45

changes in the way the individuals use the environment - populations rarely meet due to different uses of the environment and how they live within the same environment eg - nocturnal animals

Question 46

How do pops change temporally due to sympatric isolation?

Answer 46

animals and plants can go into season at different times of the year which make them less compatible with their mates eg - dogs going into season plants have different times of the year which they flower

Question 47

Describe allopatric speciation

Answer 47

1. variation is due to mutations 2. different habitats/ populations have different environmental conds and selections pressures 3. reproductive isolation 4. change in frequency of alleles 5. eventually diff species can no longer interbreed to produce fertile offspring