Entire Topic 7

Question 1

Describe:
1.Genotype
2.Phenotype
3.Homozygous
4.Heterozygous

Answer 1

1. Genotype = genetic constitution of an organism
2. Phenotype = the expression of the genes and its interactions with the environment
3. Homozygous = a pair of homologous chromosomes carrying the same alleles for a single gene
4. Heterozygous - a pair of homologous chromosomes carrying two different alleles for a single gene

Question 2

Describe:
1. Recessive allele
2. Dominant allele
3. Codominant
4. Multiple Alleles

Answer 2

1. Recessive - an allele only expressed if no dominant allele is present
2. Dominant - an allele that will always be expressed in the phenotype
3. Codominant - both alleles are equally dominant and expressed in the phenotype
4. Multiple alleles - more than 2 alleles for a single gene

Question 3

Describe:
1. Sex linkage
2. Autosomal linkage
3. Epistasis
4. Monohybrid
5. Dihybrid

Answer 3

1. Sex linkage - a gene whos locus is on the X chromosome
2. Autosomal linkage - genes that are located on the same chromosome
3. Epistasis - when one modifies or masks the expression of a different gene at a different locus
4. Monohybrid - genetic inheritance cross of a characteristic determnined by one gene
5. Dihybrid - genetic inheritance cross for a characteristic determined by 2 genes

Question 4

Cows can be red, white or roan in colour. Red and white are both dominant. If 2 roan cows reproduce, what is the probability they will produce red offspring

The parents genotypes: C^RC^W x C^RC^W

Answer 4

25%

Question 5

What do you need in genetic crosses to get all the marks?

Answer 5

1. Parental phenotype
2. Parental genotype
3. Possible gametes
4. Possible offspring
5. Offspring phenotype
6. Proportion of each phenotype

Question 6

1.What is autosomal linkage?
2. How is it possible for scientists to get results such as 300,23,17,112?

Answer 6

1. Two genes are located on the same chromsome
   - therefore alleles on the same chromsome will be inherited together because they are pulled together in meiosis - this could result a different ratio than expected
2. This is because crossing over occured during meiosis to make new combos of gametes:
   a. as 2 dominant are on the same chromosome, and 2 recessive alleles are on the same chromosome, crossing over may have occured where recessive and dominant may cross over, and that part of the chromatid may break and exchange, therefore meaning there are 4 possible gametes produced

Question 7

Corn can be purple and yellow and smooth and wrinked. These are determined by genetics.
Using the result of punnet square and by counting the actual number of each type of corn kernel, you can use chi squared to see if there is a difference between the expected and observed frequency - the student saw 21 purple kernels and 13 yellow kernels

Answer 7

1. draw the punnet square to see a 3:1 purple: yellow ratio
2. Null hypthesis: there is no significant difference between the expected and observed frequency of colour of corn kernels
3. (Observed- expected)^2/Expected for both purple and yellow, the sum is chi squared: 3.176
4. Degree of freedom: 2-1 = 1
5. Compare chi squared value to critical value: 6.176<3.841 - more than 5% probability that the results are due to chance
6. The null hypothesis is accepted - there is no significant difference between observed and expected results

Question 8

What is the hardy weinber principle used for
What is:
1. the gene pool?
2. Population
3. Allele frequency

Answer 8

equation - used to predict allele frequency in a population
1. Gene pool - ALL the alleles within a population at one time
2. Population - all the individuals of one species in one area at one time
3. Allele frequency - the proportion of an allele within the gene pool

Question 9

what are the 2 equations of hardy weignbergs principle?

Answer 9

p^2 + 2pq + q^2 = 1
p+q = 1

Question 10

1.What can variation be caused by?

2.What is disruptive selection? What can this result?

Answer 10

1. Mutation, random fertilisation of gametes
2. Disruptive selection - when individuals which contain alleles which code for an extreme trait are more likely to survive and pass on their alleles.
   Therefore allele frequency changes and more individuals possess the extreme trait allele, and the middling trait allele becomes less frequenct - continued disruptive selection can ultimately lead to speciation

Question 11

1. What is speciation and how does it occur?
2. What can the above result in each of their gene pools?

Answer 11

1. Speciation - the process which results in the creation of a new species - it can occur when one original population of the same species becomes reproductively isolated - there are now 2 populations of the same species however they cannot breed together
2. Therefore this can result to an accumulation of differences in their gene pools to such an extent that both populations would be unable to interbreed to make fertile offspring - this is classed as 2 different species

Question 12

1. Describe what occurs in allopatric speciation

Answer 12

1.Allopatric:
- populations can become seperated geographically therefore leading to reproductive isolation
-this makes these 2 populations unable to reproduce
- Both seperate populations will continue to accumulate different beneficial mutations overtime to help them survive, which may vary
- Therefore 2 populations become genetically different that they are unable to interbreed to create 2 offspring, now they are classified as 2 different species

Question 13

Describe what occurs in sympatric speciation

Answer 13

Sympatric:
- populations can become reproductively isolated because of differences in behaviour
- individuals from same species are not seperated by geographical barriers, however are unable to reproduce.
- this could be because of a random mutation which could impact reproductive behaviour, e.g. different courtship ritual, temporal, gametic, behavioural, ecological polyploidy, mechanical
- Therefore no gene flow between 2 groups
- Overtime they become reproductively isolated and accumilate different muations to such an extent they cannot interbreed to create fertile offspring
- therefore they are classed as 2 different species

Question 14

What is genetic drift and how could this lead to evolution?

Answer 14

Genetic drift: change in allele frequency within a population between generations
- continual, substantial genetic drift results in evolution
- the smaller the population the bigger the impact allele frequency changes

Question 15

What is:
1. Population
2. Habitat
3. Community
4. Ecosystem

Answer 15

1. Population - group of organisms of the same species living in the same habitat
2. Habitat - part of an ecosystem in which particular organisms live
3. Community - all the populations of different species in the same area t the same time
4. Ecosystem - A community and the non-living components of an environment

Question 16

What is:
1. Niche
2. Carrying capacity
3. Abiotic factors
4. Biotic factors

Answer 16

1. Niche - an organisms role within an ecosystem - this includes their position in the food web and habitat
2. Carrying capacity - the max pop. size an ecosystem can support
3. Abiotic factors - non living conditions in an ecosystem
4. Biotic factors - impact of the interactions between organisms

Question 17

Give examples of abiotic factors and the correlation of abiotic factors with range of species

Answer 17

1. examples: temp, O2 and CO2 conc., light intensity, pH and soil conditions
2. Less harsh the abiotic factors, such as plenty water and light, the larger the species and larger the pop sizes

Question 18

Explain these biotic factors which can affect pop size:
1. interspecific competition
2. Intraspecific competition

Answer 18

1. Interspecific competition - members of different species compete for the same resources in limited supply
2. Intraspecific competition - Members from the same species are competing for the same resources and for a mate

Question 19

In a graph which is related to predator prey relationships, what would the graph show to say that everything is normal?

Answer 19

• size of both predators and prey fluctuate
• always more prey than predators
• the size of pop will always change in the prey than the predator

Question 20

Why do we sample and how do make it as accurate as possible?

Answer 20

It is more time efficient and if implemented correctly it can be accurate
- To represent the population, we use random sampling to eliminate bias, use line transects to examine change over distance and have a large sample

Question 21

1. Explain how to do random sampling
2. Explain how to do the line transect method

Answer 21

1. a. Lie 2 tape measures at right angle to create a gridded area
   b. use random num generator to generate 2 co ords
   c. Place quadrat and collect data
   d. Repeat at least 30 times and calculate mean
2. a. Example you place a tape measure at right angles toi the shore line
   b. place the quadrat every 5 metres
3. collect the data
4. Repeat by placing another 30 transects along the beach at right angles on the shore line

Question 22

1. Describe the mark-release-recapture method

Answer 22

1. Initial sample of population is captured
2. These individuals are marked and the number caught is recorder - mark must be weather resistant
3. Marked individuals are released and left for a period of time to allow them to randomly disperse throughout their habitat
4. 2nd sample is captured
5. Total number captured in 2nd sample and the number recaptured is recorded
6. Size of population is then estimated
   The more times this is repeated the more accurate it is

Question 23

1. What is the equation of mark release recapture
2. What must you make sure of capturing techniques

Answer 23

1.(Number of organisms initially caught x number of organisms in the second sample )/ (number of organisms recaptured)

2. How you capture and mark must not cause permanent harm ,e.g. must not be toxic or increase chances of predation or decrease chances of reproduction

Question 24

1. What is succession?
2. What is the proocess of primary succession?

Answer 24

1. The change in ecological community over time
2. a. Primary succession stars where pioneer spieces colonise rock or sand
   b. these pioneer species such as lichen are adapted to survive in harsh abiotic factors and through their death and decomposition, these change the abiotic factors to less harsh and forma thin layer of soil - humus
   c. Mosses and smaller plants can now survive, and they further increase the depth and nutrients within the soil - this continues and abiotic factors become less harsh and larger plants can now survive and change the environement further
   d. Each new species may change the environment in such a way that its less suitable for the previous species, each existing species are outcompeted by the new species
   e. The final stage in a succession is known as the climax community and this is dominated by trees

Question 25

Describe the seconday succession

Answer 25

In this succession is disrupted and plants are destroyed

Succession restarts but soil is already created so it does not start from bare rock stage

Question 26

Give 6 examples of prezygotic speciation

Answer 26

Pre-zygotes
1.Temporal - Breeding seasons of each populations do not coincide
2. Gametic - gametes may change so unable to fuse
3.Behavioural - differences in mating rituals

1. Ecological -May inhabit different habitats within the same area, e.g. in the water and one in the field
2. Polyploidy: individual may have more than 2 copies of each chromosome - these individuals cannot reproduce with a normal chromosome number
3. Mechanical - differences in the anatomy of different organism prevent them mating

Question 27

Give examples of postzygotic speciation

Answer 27

1. Inviable zygote - gametes of 2 organisms from the same species combine but zygote produce may come be produced incorrectly
2. Hybrid of offspring - An offspring is produced but in sterile