Speciation

Question 1

Define speciation

Answer 1

The formation of a new species

Question 2

Define hybridisation

Answer 2

The production of offspring as result of sexual reproduction between individual from two different species

Question 3

Define allopatric speciation

Answer 3

Speciation that occur when population are physically or geographically separated and there can be no interbreeding or gene flow between the population

• geographical separation
• prevent breeding
• different habitat
• evolve adapt

The proportion of different genotype in each population changes independantly of each other
—> individuals develop adaptation according to their local conditions

Over time, the oopulation may become so genetically different that they are unable to interbreed to produce fertile offspring - separate specie

Question 4

Sympatric speciation

Answer 4

Speciation that occurs between population of a species in the same place; they become reproductively separate by mechanical, behavioural or seasonal mechanism; gene flow continues between the population to some extent as speciation occurs.

Reproductive separation
Biochemical change
Physical change

Question 5

Define founder effect

Answer 5

The loss of genetic variation that occurs when a small number of individual become isolated, forming a new population with allele frequencies not representative of the original population

Question 6

Define population bottleneck

Answer 6

The effect of an event or series or series of events that dramatically reduces the size of a population , resulting resulting in large changes in allele frequencies and a reduction in genetic diversity

Question 7

Define genetic drift

Answer 7

Change in allele frequncy within a population between generation

Happens to all population

Has drastic effwct in amall poplation

Driven by chance ,not selection

Question 8

Properties of genetic drift

Answer 8

Happens to all population

Has drastic effect in small population

Driven by chance, not selection

Two main types: founder effect and bottleneck effect

Question 9

Define selection pressure

Answer 9

The effect of one or more environmental factors that determine whther an organism will be more or less sucessful at surviving and reproducing: selection pressure drives speciation

Question 10

What cause selection pressure

Answer 10

-disease
-competition
—> food
-predation

Question 11

Propterties of allopatric speciation

Answer 11

1) separated population unable to reproduce to the physical barrier
2) the separated population have different environment/selection pressure, so will accumulate different beneficial mutation over time to help them survive. This leads to differential reproductive success so change in allele frequncy
4) the two population eventually become so geentically different that they cant reproduce to produce fertile offspring (reproductive isolation) so are classed as different species

Question 12

Properties of sympatric speciation

Answer 12

Random mutation could interfere reproductiove behavior eg individual fertile at different times of year or different courtship behaviour

Individual will not reproduce togther

Over time, their DNA becomes so different so individual are no longer able to reproduce to produce fertile offspring , so are closed as 2 different species

Question 13

Geographical isolation

Answer 13

By a physical barrier such as river

Question 14

Ecological isolation

Answer 14

Two population inhabit the same region, but develop preferences for different parts of the habitat

Question 15

Seasonal isolation

Answer 15

The timing for flowering or sexual receptiveness differs for two different species

Occurs when the breeding season of two population dont coincide

Over time the population may become so genetically different that they are unable to interbreed to produce fertile offspring
—> separate specie created

Question 16

Steps for allopatric speciation

Answer 16

1] new habitat due to separation
2) different selection pressures
3) different allele selected
Those with the allele are more likely ro survive and reproduce
4) change in allele frequency in the gene pool
5) characteristic are accumulated until a new specie is formed

Question 17

Properties of sympathic speciation

Answer 17

—> occurs within same habitat

-mating preference, disruptive selection

Question 18

Natural selection process

Answer 18

Random mutation give rise to new allele

Each species reproduces and offspring show variation

Due to selection pressure(there is a lot of competitions between these offspring) from environement individuals with beneficial allele are more likely to survive and reproduce and pass on their advantageous allele

This process repeats over mant generation

The frequency of the advantageous allele therefore increase in the population

Question 19

Evolution definition

Answer 19

The formation of new species from pre-existing species over time, as a result of changes to gene pools and allele frequencies from generation to generation

Question 20

Allopatric process

Answer 20

This creates two populations of the same species who are reproductively separated from each other, and as a result, no genetic exchange can occur between them
If there are sufficient selection pressures acting to change the gene pools (and allele frequencies) within both populations then eventually these populations will diverge and form separate species
The changes in the alleles/genes of each population will affect the phenotypes present in both populations
Over time, the two populations may begin to differ physiologically, behaviourally and morphologically (structurally)

Question 21

Sympatric process

Answer 21

Sympatric speciation takes place with no geographical barrier
A group of the same species could be living in the same place but in order for speciation to take place there must exist two populations within that group and no gene flow occurs between them
Something has to happen that splits or separates the two populations:
Ecological separation: Populations are separated because they live in different environments within the same area
For example, soil pH can differ greatly in different areas. Soil pH has a major effect on plant growth and flowering, so a population growing in soil with a slightly different pH may flower at a different time from another population, leading to reproductive separation (and eventually genetic isolation) of the two populations
Behavioural separation: Populations are separated because they have different behaviours
For example differences in feeding, communication or social behaviours, such as courting behaviours to attract a mate

Question 22

Example of sympatric

Answer 22

A species of fish lives in a lake
Some individuals within the population feed on the bottom while others remain higher up in the open water
The different feeding behaviours separates the population into different environments
Here, behavioural separation has led to ecological separation
The separated groups experience different selection pressures
Long jaws are advantageous for bottom-feeding whereas shorter jaws are advantageous for mid-water feeding
Over time natural selection causes the populations to diverge and evolve different courtship displays
They can no longer interbreed; they are now considered separate species

Question 23

Genetic drift

Answer 23

In geographically isolated populations, differences in selection pressures can lead to changes in allele frequencies, and eventually to speciation due to evolution via natural selection
However, evolution can also occur via genetic drift
This is when chance (instead of environmental selection pressures) affects which individuals in a population survive, breed and pass on their alleles
For example, when a population is significantly small, chance can affect which alleles get passed onto the next generation
Over time, some alleles can be lost or favoured purely by chance
When there is a gradual change in allele frequencies in a small population due to chance and not natural selection, genetic drift is occurring
In large populations, genetic drift is less likely to have an effect because any chance variations in allele frequencies usually even out across the whole population
Natural selection has a much more influential role in the evolution of large populations

Question 24

Genetic drift

Answer 24

When a population is significantly small, chance can affect which alleles get passed onto the next generation
Over time some alleles can be lost or favoured purely by chance
When there is a gradual change in allele frequencies in a small population due to chance and not natural selection then genetic drift is occurring

Question 25

Founder effect

Answer 25

The Founder effect occurs when only a small number of individuals from a large parent population start a new population
As the new population is made up of only a few individuals from the original population only some of the total alleles from the parent population will be present
In other words, not all of the gene pool is present in the smaller population
A gene pool is the complete range of DNA sequences (alleles) that exist in all the individuals of a population or species
Which alleles end up in the new founding population is completely up to chance
As a result, the changes in allele frequencies may occur in a different direction for the new small population vs the larger parent population

Question 26

Bottleneck effect

Answer 26

It occurs when a previously large population suffers a dramatic fall in numbers
A major environmental event can massively reduce the number of individuals in a population which in turn reduces the genetic diversity in the population as alleles are lost
The surviving individuals end up breeding and reproducing with close relatives

Question 27

Result of natural selection

Answer 27

Selection pressure produce a gradual change in allele frequencies over several generation

Question 28

Result of founder effect

Answer 28

Changes in allele frequencies occur in a different directiob for a newly isloated small popullation in comparison to the larger parent population due to chance

Question 29

Genetic drift results

Answer 29

Gradual change in allele frequencies in a small population due to chance and not natural selection

Question 30

Bottleneck effect result in

Answer 30

Reduction in the gene pool of a population due to a dramatic decrease in population size

Question 31

Genetic bottleneck

Answer 31

When an event or series of events drastically reduced the size of the population through the death of many organism

-severe decrease in the gene pool of the population
-many of the gene variant present in the original population are lost
—> so the gene pool shrink and the allele frequency shrink

Genetic diversity is reduced

Question 32

Founder effect

Answer 32

Loss of genetic variation that occurs in small number of individuals that leaves the main population and set up a new population producing voluntary ‘population bottlenecks’.

The allele carried by the individual who leave the main population may be a random selection of the gene pool but is unlikely will include all the allele or same frequency as in the original population

Question 33

Allopathic speciation

Answer 33

geographical isolation

• population of species split and move to different areas
• each new population experiences different selective pressures –> features change over time, mutations occur
• when the different populations are reintroduced, they can no longer interbreed
• -> new species have evolved

Question 34

Sympatric speciation

Answer 34

• ecological and behavioural separation
• sympatric speciation usually occurs through polyploidy

polyploidy organism: has more than 2 complete sets of chromosomes
happens when meiosis goes wrong when forming gametes
tetraploidy: 2+2 = 4; tetraploids are often sterile as 4 sets of chromosomes try to pair up during Meioisis I and get muddled up –> can reproduce asexually; usually happens in plants
triploidy: 1+2 = 3; triploidy are always sterile as 3 sets of chromosomes can not be shared evenly between daughter cells
the original diploid plant and tetraploid plant can no longer interbreed –> new species formed

Question 35

Evidence for evolution Fossil

Answer 35

Shows gradual changes
Shows intermediate
Can be dated

Question 36

Evidence for evolution

Answer 36

Changes in base sequence

Question 37

Evidence for evolution

Answer 37

Proteins

Cytochrome