topic 7 population/evolution/ecosystems

Question 1

Mutation is one cause of genetic variation in organisms.
Give two other causes of genetic variation.{2}

Answer 1

. crossing over

. independent segregation /assortment (of homologous chromosomes)

. random fusion of gametes
OR
Random fertilisation;

Question 2

What is meant by the term phenotype? {2}

Answer 2

. expression / appearance / characteristic due to) genetic constitution / genotype /
allele(s);

. Expression / appearance due to enviromwnt environment;

Question 3

In genetic crosses, the observed phenotypic ratios obtained in the offspring are often not
the same as the expected ratios.

Suggest two reasons why {2}

Answer 3

. small sample size;
2. Fusion/fertilisation of gametes is random;
Ignore breeding is random
3. Linked Genes;
Accept crossing over / sex linkage
4. Epistasis;
5. Lethal genotypes;

Question 4

In fruit flies, the genes for body colour and wing length are linked.

Explain what this means {1}

Answer 4

.(Genes / loci) on same chromosome

Question 5

why use chi squared test {1}

Answer 5

. Categorical data.

Question 6

D= dominant r= recessive

grey body (D) long wing(D)= 975
black body(r) short wing(r)= 951
grey body(D) short wing(r)= 159
black body(r) long wing(D)= 140

Use your knowledge of gene linkage to explain these results. {3}

Answer 6

. dominant genes are linked to same chrmzn, recessive genes are linked to same chrmzn

.crossing over occurs

. which produces less (D)(r) phenotypes

Question 7

What is a gene pool? {1}

Answer 7

. all the alleles in a population

Question 8

Lord Howe Island in the Tasman Sea possesses two species of palm tree which have arisen via sympatric speciation.The 2 species diverged from each other after the island
was formed 6.5 million years ago. The flowering times of the two species are different.

Using this information, suggest how these two species of palm tree arose by sympatric speciation {5}

Answer 8

. occurs in the same habitat / environment / population;

.mutation/s cause different flowering times;

. reproductive separation / isolation
OR No gene flow OR Gene pools remain separate

. different allele/s passed on / selected OR Change in frequency of allele/s
. disruptive (natural) selection;

. eventually different species cannot (inter)breed to produce fertile offspring;

Question 9

There are 9 subspecies of giraffe. These subspecies evolved when populations of giraffe were
separated for long time periods. Each subspecies has distinct coloured skin markings. Some
biologists have suggested that up to 6 of these subspecies should be classified as different
species.

(a) Explain how different subspecies of giraffe may have evolved from a common ancestor.
Use information from the passage in your answer.

Answer 9

No interbreeding / gene pools are separate / geographic(al) isolation;
Accept: reproductive isolation as an alternative to no interbreeding.
2. Mutation linked to (different) markings/colours;
3. Selection/survival linked to (different) markings/colours;
4. Adapted organisms breed / differential reproductive success;
Note: ’passed on to offspring’ on its own is not sufficient for
reproduction.
5. Change/increase in allele frequency/frequencies;

Question 10

Suggest reasons for conserving woodlands {5}

Answer 10

. conserving/protecting habitats/niches

. conserving/protecting species/maintains/increases diversity

. reduces global warming/climate change

. source of med/chemicals/wood
Reduces erosion/eutrophication

Question 11

Explain the increase in the diversity of birds as the woodland developed (3)

Answer 11

.Greater variety/diversity of plants/insects/more plant/insect species

.More food sources/more varieties of food

.More habitats/niches

Question 12

ALLOPATRIC SPECIATION 8 POSSIBLE POINTS

Answer 12

.Geographical isolation

.Separate gene pools / no interbreeding / gene flow (between populations);
Accept: reproductive isolation

.Variation due to mutation;

.Different selection pressures / different abiotic / biotic conditions / environments / habitats;

.(Different/advantageous) ALLELE(S) passed on/selected

.Different(ial) reproductive success / selected organisms (survive and) reproduce

.Leads to change / increase in allele frequency

.(Eventually different species) cannot (inter)breed to produce fertile offspring

Question 13

Reasons why observed phenotype ratios are often not the same as expected ratios {3}

Answer 13

. random fertilisation of gametes

. small sample size

. lethal alleles/genotypes

. linked genes

. epistasis

Question 14

Describe one way in which scientists could find out whether animals from 2 different populations belong to the same species. {2}

Answer 14

.breed together;

.if fertile offspring, then same species

Question 15

Mark release recapture (4)

Answer 15

. Capture / collect sample, mark and release;

. Method of marking does not harm lizard / affect survival / make it more visible to predators;

. Leave sufficient time for lizards to (randomly) distribute (on island) before collecting a second sample;

. (Population =) number in first sample × number in second sample divided by number of marked lizards in second sample / number
recaptured.

Question 16

The scientists concluded that the results shown in Figure 1 were due to succession taking
place.

explain how you can tell succession has taken place {4}

Answer 16

. invcrease in species richness

. an animal type becomes the pioneer (species);

.Pioneers species change the (abiotic) environment/habitat/conditions/factors;

. (So) less hostile for named species
OR (So) more suitable for named species;

Question 17

Give two features of a climax community {2}

Answer 17

1. Same species present (over long time)
2. Abiotic factors are constant (over time)
3. Populations stable (around carrying capacity

Question 18

Give two conditions for results from mark-release-recapture investigations to be
valid {2}

Answer 18

Marking is not removed / marking does not affect survival / predation;

2. Limited / no immigration / emigration;
3. Sufficient time for (marked) individuals to mix (within the population);
4. No / little births / deaths / breeding;
5. Sampling method is the same;

Question 19

Describe and explain how succession occurs. {4}

Answer 19

1. (Colonisation by) pioneer species;
2. Pioneers/species/organisms change the environment / habitat/ conditions/ factors;
3. Environment less hostile for
   other/new species
   OR
   (Environment becomes) more suitable for
   other/new species
   OR
   (Environment becomes) less suitable for
   previous species;
4. Change/increase in diversity/biodiversity;
5. (To) climax community;