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BIOL114 > Reproduction > Flashcards

Reproduction Flashcards

1
Q

What is sexual reproduction

A

The creation of offspring by fusion of a male gamete and female gamete to form a zygote

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2
Q

Asexual Reproduction

A

Creation of offspring without the fusion of egg and sperm

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3
Q

4 types of asexual reproduction

A

Fission, Budding, Fragmentation, Parthenogenesis

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4
Q

What is fission and what animals use it

A

Adult organisms can simply split and divide into two individuals. These individuals can then move apart and continue living
- Cnidarians

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5
Q

What is Budding and what animals use it

A

Form of asexual reproduction where a bud forms that develops into an adult and breaks away from the main body
- Hydra

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6
Q

Fragmentation

A

This is an emergency form of reproduction where and adult undergoes physical trauma and regenerates after this - forming body from cinched head/tail.
- Planaria, Sea urchin/stars

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7
Q

Parthenogenesis

A

No fertilisation of female gamete. Offspring are identical to their mother (clones) as the egg alone is sufficient to develop into an adult organism
- Some lizards, hymenopterans, aphids, spiders, molluscs, fish

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8
Q

Clone

A

Group of genetically identical individuals from the same parent

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9
Q

What is an allele

A

Particular gene variant at a locus

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10
Q

What is phenotype determined by

A

The sum of an individuals alleles

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11
Q

What is a locus

A

A genes specific position along a chromosome

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12
Q

What are genes

A

Units of heredity that are made up of DNA segments

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13
Q

Diplod cell

A

2 copies of each chromosome

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14
Q

Haploid

A

1 copy of each chromosome

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15
Q

What is fertilization

A

Union of gametes

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16
Q

Why is meiosis required in sexual reproduction (not involving variation)

A

In sexual reproduction, meiosis is required to halve the amount of DNA in the gametes so that the amount of DNA after fertilisation is diploid, the required condition for all somatic ells

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17
Q

Two important changes in meiosis compared to mitotic reproduction

A
  • Change in ploidy: go from diploid to haploid
  • End up with 4 genetically different daugjter cells
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18
Q

3 aspects of fertilisation/meiosis that are responsible for variation

A

Independent assortment
Crossing over
Random fertilisation

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19
Q

What is independent assortment

A

Homologous pairs of chromosomes orient randomly at metaphase I of meiosis
In independent assortment, each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs

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20
Q

What is crossing over

A

Recombining chromosomes, contributes to genetic variation by combining DNA from two parents into a single chromosome

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21
Q

What is random fertilisation

A

Any sperm can fuse with any ovum

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22
Q

How does variation arise in zygote

A

In humans, the fusion of two gametes (each with 8.4 million possible chromosome combinations from independent assortment) produces a zygote with any of about 70 trillion diploid combinations
Crossing over adds even more variation

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23
Q

Benefit of sexual reproduction

A

Increase genetic variation

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24
Q

Why is variation in heritable traits important

A

Allow adaptive evolution to occur

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25
Q

Why do sexually reproducing organisms have an advantage

A

When the environment changes rapidly, sexually reproducing organisms adapt faster than asexual organisms and thus outcompete them

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26
Q

Downside of asexual reproduction

A

Although asexual reproduction involves less energy to produce offspring, the species have a limited lifespan and will eventually die out. They eventually hit a change in their conditions that they cannot adapt to due to lack of variety between individuals

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27
Q

Monoecy/hermaphrodism

A

two sexes in the same individual

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28
Q

Dioecy

A

Specialised to produce only one type of gamete

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29
Q

Disadvantage of dioecy (3)

A
  • Less efficient as only half of offspring can produce offspring (cost of males)
    • Less efficient as energy wasted on mating (finding a mate, ensuring sperm finds egg,
  • disastrous if isolated, features can be selected for (deer antlers) that may reduces survivor hood of males but is required to gain attention from females)
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30
Q

Disadvantage of Monoecy (loss of varation)

A

1/2 of animal species that undergo monoecious reproduction show between 20 and 80% selfing rates (own sperm fertilising own eggs)
- If a male and female gamete from an individual fuse, it will get a loss of variation

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31
Q

Disadvantage of Monoecy (energetically costly)

A
  • Costly in terms of having to produce both male and female gametes (can be partially overcome by sequential hermaphrodism (switch dependant on size)
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32
Q

Main goal of sexual reproduction

A

bring egg and sperm together

33
Q

Acrosome

A

Full of enzymes which are released when worm senses the jelly coat. The enzyme digests away the jelly coat, allowing the worm to bury into the surface of the egg

34
Q

8 Step process of fertilisation

A
  1. Acrosome reaction to digest jelly
  2. Specificity via receptors on egg
  3. Binding triggers fusion of plasma membranes
  4. Need to avoid polyspermy: fast reaction via depolarization 1/10th of second
  5. Fusion also releases inositol triphosphate, causes Ca release in egg (wave)
  6. Ca wave triggers cortical vesicles to fuse with plasma membrane releasing enzymes
  7. Enzymes degrade receptors and harden vitelline membrane = slow block (10-60sec)
  8. Nucleus only is internalized and fuses with female.
35
Q

what does external fertilisation need

A
  1. Need aquatic environment to allow sperm motility and prevent drying out of egg (and zygote)
36
Q

Why does quantity assist in external fertilisation

A

More gametes released increases probability of gametes meeting and counters effect of predation

37
Q

Protective mechanism involved in external fertilisation

A

Camouflage (fish eggs are white on the bottom and black on the top)
Guarding behaviour

38
Q

How is timing involved in external fertilisation

A

Synchronisation of male and female gamete release is essential
- Environmental cues – day length, change in temperature, change in environment, usually indicating favourable season for breeding; tidal changes
Specific cues from individuals of the same species:
- In marine invertebrates (clams, sea urchins, sea cucumbers), pheromones may be involved.
- In fish and other aquatic animals with well-developed eyes, social stimulation or courtship behaviour is often important.

39
Q

Benefits of internal fertilisation

A
  • Safer for gametes
  • Fewer gametes required (less costly)
  • Synchronisation less of an issue
  • Allowed the transition to a permanent land/terrestrial habitat (found in most terrestrial animals)
40
Q

Behavioural adaptations of Internal fertilisation (3)

A
  1. Copulation (also called coitus) is the physical joining of male and female accessory sex organs to transfer sperm
  2. Multituse of behavioural mating strategies, usually stimulated by pheromones - chemical signals that females emit to signal sexual receptivity
  3. Requires a male and female to come close enough together for long enough to allow sperm transfer
41
Q

Why do male and female have different mating strategies

A

Due to the nature of their gametes: Sperm are energetically inexpensive - egg is expensive

42
Q

Why does mating behaviour originate

A
  • Due to gamete anisogamy (unequal gamete size), female has fewer gametes (eggs), each of which is more costly to produce than a male gamete, so will try to choose the best male(s) – highly selective mating behaviour.
  • Males can produce more gametes so will benefit from more mating’s – behaviour aimed at mating with as many females as possible (impress and collect females).
43
Q

Monogamy

A

Both male and female maintain single partner throughout entire mating season

44
Q

Advantage of monogamous behaviour

A

In species where the young are particularly vulnerable and may benefit from protection by both parents, monogamy may be an optimal strategy.

45
Q

Why are birds monogamous

A
  • Lay eggs that have to be kept warm (and protected)
  • Chicks need to be fed and protected after hatching
  • Too difficult for one parent so would evolve shared system that benefits both parents.
46
Q

Advantage of internal fertilisation

A

Less cost of wasting gametes, easier to get synchronisation, lower danger of eggs being eaten/damaged

47
Q

Challenge to overcome with internal fertilisation

A

Adaptations to allow adults to be bought together

48
Q

Gonads/Primary sex organs

A

Where gametes are produced

49
Q

Secondary sex organs

A

Function to ensure gametes meet

50
Q

Oviduct

A

Area where sperm is collected, where the egg travels to be fertilised

51
Q

Spermatheca

A

Insects - allows females to store sperm for up to a year

52
Q

Advantage of spermatheca

A

Allow females to wait for the right time, when conditions are favourable and health is most optimal, to fertilise the egg

53
Q

Ovary

A

Structures designed to grow the egg

54
Q

Why can sperm not fertilise the egg at all times of the monthly cycle

A

Cervix is plugged with mucus under influence of the hormone testosterone

55
Q

Vestibular gland

A

supply mucus that allows for intercourse.

56
Q

Oocyte

A

Partially developed egg

57
Q

Function of cilia in oviduct

A

Convey the egg to the uterus

58
Q

What is the endometrium

A

Uterus lining that contains many blood vessels

59
Q

What is the vagina

A

A muscular but elastic chamber that is the repository for sperm during copulation and serves as the birth canal

60
Q

Function of seminal vesicle and accessory glands

A

Supply nutrients to allow sperm to activate, swim, and supply in the reproductive tract and regulate pH

61
Q

Vas Deferens

A

Sperm travels along vas deferens, a duct which leads to the penis

62
Q

Secondary sex organs in males

A

vas deferen, urethra,

63
Q

Why are male primary gonads stored outside the main body

A

Temperature regulation

64
Q

Function of uterus

A

Specialised part of oviduct to allow for internal embryo development

65
Q

Intromittent organ

A

Structure that enters female reproductive tract and deposits sperm

66
Q

Aedeagus

A

insect penis

67
Q

How does female choice lead to rapid evolution of genitalia

A

Choose males with genitalia that best stimulate them during copulation of fit better - thus sons will have superior mate-attracting potential (by better female stimulation).

68
Q

How does sperm competition lead to evolution of male genitalia

A

For females that display promiscuity, when the ejaculates of two or more males compete to fertilise an ovum.

69
Q

Example of sperm competition

A

In dragon selection has favoured males with genitalia that remove rival sperm from the female.

70
Q

Dragonfly penis adaptation

A

Dragonflies penis has a brush to brush out any sperm that is already present

71
Q

Molluscs/sea slug copulation

A
  • 2 penises which fertilise each other
    • Sperm pumping takes about 10 minutes
    • Then the sea slugs will separate
    • They do not retract their penis, and their penis will break off inside the other individual
    • Penis has spikes going backwards that prevent it from leaving the reproductive tract
  • This prevents another sea slug from depositing their sperm
  • Can keep having intercourse until they run out of penis
72
Q

2nd male advantage

A

2nd male physically dislodges stored sperm via adaptation and or via fluid accompanying sperm

73
Q

Sexual conflict

A

Sexual selection that only benefits males - Favours traits that increase the fitness of one sex even when it is costly to the other

74
Q

Examples of sexual conflict in vertebrates

A
  • In many reptiles, fish and felines, the male may have hooks or bards on or near his penis that attach to the female during copulation
  • Dog penises also swell during copulation and are difficult to remove until completion
  • Sharks have been known to severely bite females to hold them during copulation
75
Q

Why do female birds only possess one gonad

A
  • Adaptation for flight, get rid of excess weight
76
Q

Do birds have an intromittent organ

A

No

77
Q

How have birds evolved to copulate

A

Have evolved behavioural adaptations so they are able to bring the cloaca and can manage to mount each other and connect cloaca

78
Q

How do male ducks reproduce

A

They evolved huge “ballistic” penises that are different from mammalian ones - being lymph filled and rapidly everted directly into the female ducks vagina

79
Q

How have ducks evolved to counter forced mating

A

Can only let left handed corkscrew properly into vagina once the female relaxes and allows the entry of the penis - only happens with wanted & consenting sex

BIOL114 (14 decks)

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