component 2 exam errors

Question 1

) In a cross between two individuals with the genotype DdEe, where the genes D and E are on the same chromosome, the offspring showed four different types of phenotype.
The phenotype of some of the offspring was far more common than expected and some phenotypes
were very rare. Explain these observations.

Answer 1

this occurred due to crossing over in meiosis, as alleles were exchanged between chromosomes.

crossing over is however very rare, so phenotypes that came about due to it were very rare as well

incomplete linkage

genes were further apart on the same chromosome

recombinants were equal in number

Question 2

In terms of insect pollination , how is the effective transfer of pollen ensured ?

Answer 2

Effective transfer of pollen is ensured when the anther and the stigma touch the same part of the insect

Question 3

How is self pollination avoided

Answer 3

By the anther and the stigma maturing at different times

Question 4

Function of the generative male nucleus

Answer 4

For fertilisation

Question 5

Function of the tube nucleus

Answer 5

It controls the growth of the pollen tube

Question 6

Features of a wind pollinated flower

Answer 6

Small petals
They have no nectar
That have feathery stigmas
They are not scented
Petals are dull

Question 7

State how the production of pollen grains has enabled flowering plants to adapt to terrestrial life

Answer 7

Pollen tube delivers male gametes to the egg

This stops the risk of dehydration of gametes

Leads to the formation of a tough exine or outer wall

Question 8

Part of the flower that develops into the testa

Answer 8

Integuments

Question 9

Part of the flower that develops into the embryo plant

Answer 9

Zygote

Question 10

Why is a wheat grain considered more as a fruit than as a seed

Answer 10

Because seeds only have testas , but the grain has an endosperm and embryo

A fruit retains the ovary wall unlike a seed , which is what a wheat grain does

Question 11

Explain why events taking place in the embryo sac of a wheat flower are described as double fertilisation

Answer 11

One nucleus fuses with the ovum , and the other fuses with the polar nuclei

The first forms the zygote and the second forms the triploid endosperm nucleus

Question 12

genetic drift

Answer 12

a process of random fluctuations in the frequency of alleles in a populations

Question 13

founder effect

Answer 13

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

Question 14

when organisms of the same species are put in different habitats over a long period of time, explain why they eventually evolve into separate species

Answer 14

they are geographically isolated

so over time, they develop adaptations that prevent them from successfully breeding with the original population

courtship behaviour

Question 15

suggests pieces of evidence that can be used to identify organisms of the same species

Answer 15

they share the same gene pool

similar behavior

similar genetic profile

similar morphology

similar proteins

Question 16

suggest possible isolating mechanisms

Answer 16

mechanical isolation

courtship behavior

behavioral isolation

Question 17

dogs and foxes have different number of chromosomes
rare cases of mating between both species to produce a “dox” has been recorded. The dox is never sterile, give the reasons for this sterility

Answer 17

chromosomes are not homologous

so they cannot form bivalents during prophase 1 of meiosis

meiosis does not occur

so they cannot produce gametes

Question 18

uterus wall also known as

uterus lining is also known as the

Answer 18

myometrium

endometrium

Question 19

suggest why only one functional female gamete is produced as a result of meiosis

Answer 19

polar bodies are produced
functional gametes retain most of the cytoplasm, which acts as a food store for the zygote until implantation occurs

Question 20

blastocyst

Answer 20

hollow ball of undifferentiated cells that the zygote divides to form

Question 21

state how the secondary oocyte usually prevents polyspermy and suggest a reason why there is an increased risk of polyspermy with IVF

Answer 21

the cortical reaction occurs to form a fertilization membrane, thereby preventing the entry of any more sperm

secondary oocyte that is taken from the Graafian follicle during IVF is immature, so it cannot form a fertilization membrane

Question 22

the developing embryo is not transferred into the uterus until three days after IVF. explain why this delay is needed using your knowledge of fertilization and implantation

Answer 22

to allow the cleavage to form

if the embryo is put into the uterus immediately, the endometrium would not be fully developed

trophoblastic villi will not have developed so HCG will not be produced

so the embryo would not implant

Question 23

give two reasons why there must be a barrier between fetal and maternal blood systems

what serves as this barrier

Answer 23

to protect the foetus from the mother’s immune system

protection against differences in pressure in the mother’s blood

serves as a barrier against toxic substances in the mother’s blood

the placenta

Question 24

suggest how pressure differences in the uterine arteries and the intervillous space allow the placenta to carry out its function

Answer 24

pressure differences force materials through the capillaries in the placenta

Question 25

suggest how having LONG capillaries in the placenta allows the placenta to carry out it’s function

Answer 25

provides a large surface area for exchange between foetal and mother’s blood

Question 26

state four differences between the composition of blood in the umbilical arteries and the umbilical vein

Answer 26

Umbilical artery:
less oxygen
more carbon dioxide
more urea
less nutrients
less antibodies

umbilical vein:
more oxygen
less carbon dioxide
less urea
more nutrients
more antibodies

Question 27

Functions of the nucellus

Answer 27

Contains cells that provide nutrition for the growth of the ovule

Question 28

Dormancy

Answer 28

Period of suspended growth and metabolism that allows the seed to wait for favourable conditions before germinating

Question 29

Why does the seed become dormant

Answer 29

To increase it’s chances of survival and successful germination

Question 30

Phylogeny

Phylogenetics

Answer 30

Evolutionary relationships between organisms

Study of the evolutionary relationships between organisms

Question 31

Advantages of having a phylogenetic tree

Answer 31

They can show the evolutionary relationships between organisms

They show evolutionary timeline( as we go up the phylogenetic tree, we get closer to the present time )

They are continuous

Question 32

Difference between functions of Dna polymerase and dna liga se

Answer 32

Polymerase joins individual nucleotides together working along a template strand while ligase joins dna fragments together at singular points in genetic engineering

Question 33

What is hierarchy in classification systems

Answer 33

It is when smaller groups are arranged within larger groups
There is no overlap between the groups

Question 34

Modern classification methods

Answer 34

Dna sequence
mRNA sequence
Amino acid sequence

Question 35

In a t test , what do we do when the our value is greater than the critical value

Answer 35

In a t-test, the critical value is the value of t that separates the rejection region from the non-rejection region. If the calculated value of t is greater than the critical value, it means that the difference between the means of the two groups being compared is statistically significant. This indicates that the probability of obtaining the observed difference by chance is very low, and that the difference is likely due to a real difference between the two groups. Therefore, if the calculated value of t is greater than the critical value, we reject the null hypothesis and conclude that there is a significant difference between the means of the two groups being compared.