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Advanced Higher Biology > Variation and Sexual Reproduction > Flashcards

Variation and Sexual Reproduction Flashcards

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1
Q

State 2 costs of sexual reproduction

A

males are unable to produce offspring

only half of each parent’s genome is passed to offspring, disrupting successful parental genomes

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2
Q

Why do the benefits of sexual reproduction outweigh the costs

A

Due to the increase in genetic variation in the population

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3
Q

Why is genetic variation in offspring beneficial?

A

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

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4
Q

What would a host with a good fitness be able to do

A

They would be better at resisting and tolerating a parasite

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5
Q

What would a parasite with a good fitness be able to do

A

Those that are able to feed, reproduce and find new hosts

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6
Q

What makes asexual reproduction successful

A

Whole genomes are passed to offspring

Just one parent can produce daughter cells and establish a colony of virtually any size over time

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7
Q

In what situation/environment would asexual reproduction be beneficial

A

In very narrow and stable niches or when re-colonising disturbed habitats

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8
Q

What is parthenogenesis

A

Reproduction from a female gamete without fertilisation

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9
Q

State 2 examples of organisms that use parthenogenesis

A

Animals that lack fertilisation

Lower plants

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10
Q

In what conditions is parthenogenesis most common

A

In cooler climates (disadvantageous to parasites)

Regions of low parasite density

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11
Q

Can natural selection or evolution occur in asexually producing organisms and why?

A

Yes it can and this is possible due to mutation which provides a small degree of variation

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12
Q

What is another mechanism for increasing variation in asexually reproducing organisms and give two examples where this is possible

A

Horizontal gene transfer in bacteria and yeast

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13
Q

Why can prokaryotes evolve fast

A

They can exchange genetic material horizontally instead of vertically

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14
Q

What is meiosis

A

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

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15
Q

State the 3 features of homologous chromosomes

A

They are the same size
Same centromere position
Have the same sequence of genes at the same loci

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16
Q

Describe meiosis I (5 points)

A
  1. Chromosomes condense and homologous chromosomes pair up
  2. Chiasmata form at points of contact between non-sister chromatids of a homologous pair and sections of DNA are exchanged. (Producing different recombinant chromosomes)
  3. Spindle fibres attach to the homologous pairs and line them up at the equator of the spindle
  4. The chromosomes of each homologous pair are separated and move towards opposite poles
  5. Cytokinesis occurs and two daughter cells are produced
17
Q

What is the independent assortment

A

When each pair of homologous chromosomes is positioned independently of the other pairs, irrespective of their maternal and paternal origin

18
Q

Describe meiosis II

A

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

19
Q

What determines the sex of birds, mammals and some insects

A

The presence of sex chromosomes

20
Q

In most mammals, which gene determines the development of male characteristics

A

The SRY gene on the Y chromosome

21
Q

What do heterogametic males lack

A

most of the corresponding homologous alleles on the shorter Y chromosome

22
Q

Explain X chromosome inactivation

A

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

23
Q

What is the effect of X chromosome inactivation

A

It prevents a double dose of gene products which could be harmful to cells. This means carriers are less likely to be affected by any deleterious mutations on these X chromosomes

24
Q

How many cells within some tissue will have their X chromosomes inactivated

A

Half

25
Q

What are hermaphrodites

A

Species that have functioning male and female reproductive organs in each individual. They usually have a partner with which to exchange gametes

26
Q

What type of gametes do hermaphrodites produce

A

Both male and female gametes

27
Q

What is beneficial about hermaphrodites

A

If encountering a parter is an uncommon event, there is no requirement for that partner to be of the opposite sex

28
Q

What determines the sex in reptiles

A

The environmental temperature of egg incubation

29
Q

Name 3 factors that can cause sex change

A

Size
Competition
Parasitic infection

30
Q

What can influence the sex ratio of offspring

A

Resource availability

Advanced Higher Biology (10 decks)

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