variation and sexual reproduction

Question 1

what are the costs of sexual reproduction

Answer 1

Costs of sexual reproduction: males unable to produce offspring; only half of each parent’s genome passed onto offspring, disrupting successful parental genomes

Question 2

Benefits outweigh costs due to an increase in what

Answer 2

Benefits outweigh costs due to an increase in genetic variation in the population

Question 3

what does genetic variation provide

Answer 3

Genetic variation provides the raw material required for adaptation, giving sexually reproducing organisms a better chance of survival under changing selection pressures

Question 4

what does the red queen hypothesis explain

Answer 4

The Red Queen hypothesis to explain the persistence of sexual reproduction

Question 5

Co-evolutionary interactions between parasites and hosts may select for what

Answer 5

Co-evolutionary interactions between parasites and hosts may select for sexually reproducing hosts

Question 6

Hosts better able to resist and tolerate parasitism have what

Answer 6

Hosts better able to resist and tolerate parasitism have greater fitness. Parasites
better able to feed, reproduce and find new
hosts have greater fitness.

Question 7

If hosts reproduce sexually, what happens

Answer 7

If hosts reproduce sexually, the genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasites

Question 8

Asexual reproduction can be what

Answer 8

Asexual reproduction can be a successful reproductive strategy as whole genomes are passed on from parent to offspring

Question 9

In asexual reproduction…?

Answer 9

In asexual reproduction, just one parent can produce daughter cells and establish a colony of virtually unlimited size over time.

Question 10

Maintaining the genome of the parent is an advantage when

Answer 10

Maintaining the genome of the parent is an advantage particularly in very narrow, stable niches or when re colonising disturbed habitats

Question 11

what are examples of asexual reproduction in eukaryotes

Answer 11

Vegetative cloning in plants and parthenogenesis in lower plants and animals that lack fertilisation are examples of asexual reproduction in eukaryotes

Question 12

Offspring can be reproduced more often and in what

Answer 12

Offspring can be reproduced more often and in larger numbers with asexual reproduction

Question 13

what is Parthenogenesis

Answer 13

Parthenogenesis is reproduction from a female gamete without fertilisation.

Question 14

where is parthenogenesis more common in

Answer 14

Parthenogenesis is more common in cooler climates, which are disadvantageous to parasites, or regions of low parasite density or diversity

Question 15

what are asexually reproducing populations not able to do

Answer 15

Asexually reproducing populations are not able to adapt easily to changes in their environment, but mutations can occur that provide some degree of variation and enable some natural selection and evolution to occur

Question 16

Organisms that reproduce principally by asexual reproduction also often have mechanisms for what

Answer 16

Organisms that reproduce principally by asexual reproduction also often have mechanisms for horizontal gene transfer between individuals to increase variation, for example the plasmids of bacteria and yeasts

Question 17

what is the result of prokaryotes exchanging genetic material horizontally

Answer 17

Prokaryotes can exchange genetic material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer.

Question 18

what is meiosis

Answer 18

Meiosis is the division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte

Question 19

how do chromosomes usually appear in diploid cells

Answer 19

In diploid cells, chromosomes typically appear as homologous pairs

Question 20

what are Homologous chromosomes

Answer 20

Homologous chromosomes are chromosomes of the same size, same centromere position and with the same sequence of genes at the same loci.

Question 21

The chromosomes, which have replicated prior to meiosis I, each consist of what (meiosis 1)

Answer 21

The chromosomes, which have replicated prior to meiosis I, each consist of two genetically identical chromatids attached at the centromere

Question 22

The chromosomes condense and what happens

Answer 22

The chromosomes condense and the
homologous chromosomes pair up

Question 23

Chiasmata form at points of what?

Answer 23

Chiasmata form at points of contact between the non-sister chromatids of a homologous pair and sections of DNA are exchanged

Question 24

linked genes are what?

Answer 24

Linked genes are those on the same chromosome. Crossing over can result in
new combinations of the alleles of these
genes

Question 25

This crossing over of DNA is what

Answer 25

This crossing over of DNA is random and produces genetically different recombinant chromosomes

Question 26

Spindle fibres attach to the homologous pairs and then what (meiosis 1)

Answer 26

Spindle fibres attach to the homologous pairs and line them up at the equator of the spindle

Question 27

The orientation of the pairs of homologous chromosomes at the equator is what

Answer 27

The orientation of the pairs of homologous chromosomes at the equator is random

Question 28

define independant assortment

Answer 28

Each pair of homologous chromosomes is positioned independently of the other pairs, irrespective of their maternal and paternal origin. This is known as independent assortment.

Question 29

The chromosomes of each homologous pair are separated and do what

Answer 29

The chromosomes of each homologous pair are separated and move towards opposite poles

Question 30

Cytokinesis occurs and ...?

Answer 30

Cytokinesis occurs and two daughter cells form

Question 31

what is the start of meosis 2

Answer 31

Meiosis II Each of the two cells produced in meiosis I undergoes a further division during which the sister chromatids of each chromosome are separated

Question 32

how many haploid cells are produced (meiosis 2)

Answer 32

A total of four haploid cells are produced.

Question 33

The sex of birds, mammals and some insects is determined by the presence of what

Answer 33

The sex of birds, mammals and some insects is determined by the presence of sex chromosomes

Question 34

In most mammals the SRY gene on the Y chromosome determines what?

Answer 34

In most mammals the SRY gene on the Y chromosome determines development of male characteristics

Question 35

Heterogametic (XY) males lack most of the what? and what can this result in

Answer 35

Heterogametic (XY) males lack most of the corresponding homologous alleles on the shorter (Y) chromosome. This can result in sex-linked patterns of inheritance as seen with carrier females (XBXb) and affected males (XbY)

Question 36

In homogametic females (XX) one of the two X chromosomes present in each cell is randomly what?

Answer 36

In homogametic females (XX) one of the two X chromosomes present in each cell is randomly inactivated at an early stage of development

Question 37

X chromosome inactivation prevents a what

Answer 37

X chromosome inactivation prevents a double dose of gene products, which could be harmful to cells

Question 38

what is x chromosome inactivation

Answer 38

X chromosome inactivation is a process by which most of one X chromosome is inactivated.

Question 39

what are carriers less likely to be affected by

Answer 39

Carriers are less likely to be affected by any deleterious mutations on these X chromosomes

Question 40

As the X chromosome inactivated in each cell is random what happens

Answer 40

As the X chromosome inactivated in each cell is random, half of the cells in any tissue will have a working copy of the gene in question

Question 41

what are hermaphrodite

Answer 41

Hermaphrodites are species that have functioning male and female reproductive organs in each individual

Question 42

what do hermaphrodites produce

Answer 42

They produce both male and female gametes and usually have a partner with which to exchange gametes

Question 43

what are the benefits of hermaphrodite

Answer 43

The benefit to the individual organism is that if the chance of encountering a partner is an uncommon event, there is no requirement for that partner to be of the opposite sex

Question 44

For other species, environmental rather than what determines sex and sex ratio

Answer 44

For other species, environmental rather than genetic factors determine sex and sex ratio

Question 45

what is enviromental sex determination in reptiles controlled by

Answer 45

Environmental sex determination in reptiles is controlled by environmental temperature of egg incubation.

Question 46

Sex can change within individuals of some species as a result of what

Answer 46

Sex can change within individuals of some species as a result of size, competition, or parasitic infection

Question 47

In some species the sex ratio of offspring can be adjusted in response to what

Answer 47

In some species the sex ratio of offspring can be adjusted in response to resource availability