Unit 3- Speciation

Question 1

What is needed in order to form a new species?

Answer 1

Part of an existing population must become reproductively isolated

Question 2

Reproductive isolation can come about in 2 different ways:

Answer 2

Allopatric and sympathise speciation

Question 3

Why do 2 species not form if a species is not reproductively isolated?

Answer 3

If members of 2 groups can still interbreed then there will be gene flow between them so remaining as 1 species

Question 4

When does allopatric speciation come about?

Answer 4

When 2 populations of the same species become geographically isolated (allopatric meaning different father land)

Question 5

Give 3 causes of allopatric speciation:

Answer 5

• island drift
• formation of a mountain range
• sea level rises causing body of water barrier
• an impassable rift due to earth quake
• divided by a desert
• divided by a large distance

Question 6

Describe the stages of allopatric speciation:

Answer 6

1- there is interbreeding amongst a population of species
2- the population becomes divided by a physical barrier, so long as the 2 populations are reproductively isolated there is no gene flow between groups
3- if the environments are different the different characteristics will be selected by natural selection shifting the allele frequencies
4- if the barrier is then later removed the 2 populations are so different that they cannot interbreed to produce fertile offspring

Question 7

Does speciation occur if the 2 populations are separated by a physical barrier but the environment is identical on both sides?

Answer 7

Yes, the populations will change by random genetic mutations again shifting the allele frequency

Question 8

What is sympatric speciation?

Answer 8

When 2 populations of the same species become reproductively isolated even though they share the same geographical location (no physical barrier) (sympatric- means same fatherland)

Question 9

What different ways may 2 species become reproductively isolated?

Answer 9

• geographical isolation
• habitat isolation
• seasonal isolation
• mechanical isolation
• behavioural isolation
• gametic isolation
  (Get Horny Soon My Bumholes Gaping)

Question 10

What is habitat/ecological isolaton?

Answer 10

• when populations become reproductively isolated by developing different niches and occupying different habitats in the same environment, so do not meet to breed

Question 11

Give an example of habitat isolation

Answer 11

Fruit flies used to only live in and eat hawthorn bushes, A mutant strain of fruit fly arose that had the enzyme to digest apples, so 2 different populations arose living in the different plants occupying a different niche

Question 12

What is behavioural isolation?

Answer 12

When populations become reproductively isolated by developing different courtship behaviours, as a result not responding to the other populations displays

Question 13

What is seasonal/temporal isolation?

Answer 13

When 2 populations become reproductively isolated because the timing of their reproductive season changes

Question 14

What is mechanical isolation?

Answer 14

When populations become reproductively isolated because of a change in their reproductive organ anatomy

Question 15

What is gametic isolation?

Answer 15

When populations become reproductively isolated because the male and female gametes from2 populations are incompatible together

Question 16

Certain bacteria are growing resistant to our antibiotics, how can we counter this??

Answer 16

• reduce the use of antibiotics in humans and in food
• use DNA sequencing to identify bacteria finding new ways of targeting them with drugs and genetic engineering
• develops new antibiotics

Question 17

Summary of speciation:

Answer 17

1- a population becomes separated into 2 reproductively isolated groups
2- the 2 groups environments are different so natural selection favours different characteristics
3- the allele frequencies in the 2 groups shifts in different ways
4- the 2 populations eventually will be unable to interbreed

Question 18

What is biodiversity?

Answer 18

The variety of all life on earth

Question 19

What is included in the meaning behind biodiversity?

Answer 19

• number of different ecosystems (ecosystem diversity)
• number of species (species diversity)
• number of individuals in a species
• genetic variation within each species (genetic diversity)

Question 20

What is the gene pool of a species?

Answer 20

All the genes in that species

Question 21

Do all the members of the same species have the same genes and alleles.

Answer 21

They have the same genes but different combinations of alleles

Question 22

What is the definition of genetic diversity?

Answer 22

The number of different alleles within a species’ gene pool

Question 23

What is meant if a species has a small gene pool?

Answer 23

The species is therefore less genetically diverse (fewer alleles) eg cheetahs who are all almost genetically identical

Question 24

What may reduce genetic diversity?

Answer 24

Selective breeding, as it only selects a specific few desired alleles to be passed on the the offspring

Question 25

Farm animals and crops are often selectively bred lowering their genetic diversity, why is this bad?

Answer 25

• all susceptible to 1 disease

- susceptible to an environmental change

Question 26

What is species diversity?

Answer 26

The variety of species in a community

Question 27

What is species richness?

Answer 27

Number of species in a sample

Question 28

What is species abundance? (Same as species evenness)

Answer 28

Number of individuals in a species

Question 29

What is a good measure of species diversity?

Answer 29

Simpson’s diversity index

Question 30

What does a higher value of D (Simpson’s index) mean?

Answer 30

The greater the biodiversity

Question 31

Will deserts have a high or low Simpson’s index’s?

Answer 31

Low