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Biology > Animal Reproduction > Flashcards

Animal Reproduction Flashcards

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1
Q

What is Asexual reproduction?

A

Creation of new individuals without fusion of gametes

» Relies on mitosis at the cellular level

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2
Q

What are three different types of Asexual reproduction?

A
  • Budding
  • Fission
  • Fragmentation and regeneration
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3
Q

What is Parthenogenesis?

A

A form of Asexual reproduction where an egg develops without being fertilised
» Offspring can be haploid or diploid

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4
Q

What animals are capable of Parthenogenesis?

A

» Inverts: bees, wasps, ants, crustaceans, rotifers …
» Rarer in vertebrates (about 0.1% of species)
• Komodo dragon
• Hammerhead shark

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5
Q

What species is Parthenogenesis most important to and why?

A

Some species of lizards are exclusively females and reproduce entirely asexually by parthenogenesis
» Oddly enough, more eggs laid if mounted at ovulation … historical artefact? (evolved from sexual species?)

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6
Q

What is sexual reproduction?

A

Fusion of haploid gametes (sex cells) → diploid (“zygote”), which divides by mitosis to produce multicellular embryo
» Female gamete = egg: large, nonmotile
» Male gamete = sperm: small, motile

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7
Q

What are the advantages and disadvantages of Asexual reproduction?

A

Advantages:

  • No need to locate a mate
  • Asexual products usually large (↑ survivorship)
  • Rapid development to adult (limited vulnerable juvenile stage)
  • May occur throughout the year

Disadvantages:

  • No genetic recombination (offspring is genetic copy of parent)
  • Offspring usually locally dispersed
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8
Q

What are the advantages and disadvantages of Sexual reproduction?

A

Advantages:

  • Genetic recombination (→ adaptive)
  • Offspring often widely dispersed (eg larvae in ocean currents)

Disadvantages:

  • Need a mate
  • Sexual products usually small (↓ survivorship)
  • Delay to reach sexual maturity (longer vulnerable juvenile stage)
  • Usually occurs seasonally (when environmental conditions favour survival of offspring)
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9
Q

What is the sexual reproductive cycle?

A

Environmental cues (eg temperature, day length) → sex hormones → reproductive status

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10
Q

What is the reason for a sexual reproductive cycle and what impacts might be affecting it?

A

» So that offspring are born in most favourable conditions (eg Spring)
» Impact of climate change?
- eg Caribou in Greenland: mismatch between onset of migration (day length) and plant growth (temperature)

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11
Q

What adaptions have some animals formed when there is a scarcity of mates?

A

Finding a mate can be challenging, so some animals are hermaphrodites (have both male and female reproductive systems) → any two individuals can mate
» Some species can even self fertilise

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12
Q

What is Sequential hermaphroditism?

A

In some hermaphrodites, the animal starts out as one sex and switches to the other sex later in its life.

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13
Q

What are the two types of sequential hermaphroditism?

A

» Protogynous: female first (most common)

» Protandrous: male first

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14
Q

Provide a summary of fertilisation

A
  • Once found a mate, male gamete needs to fertilise the female gamete
  • Fertilisation = union of sperm and egg
  • Can be external or internal
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15
Q

Where does external fertilisation happen?

A

Requires moist habitat (avoid gametes from drying out, allows sperm to swim to eggs)

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16
Q

How does External Fertilisation work?

A

Gametes released into water
» Asynchronous (→ courtship)
» Synchronous (broadcast spawning)

17
Q

What is Internal Fertilisation?

A

Adaptation that enables sperm to reach the egg even in dry environment
- Requires cooperative behavior (copulation) and compatible reproductive systems

18
Q

What are the advantages and disadvantages of External Fertilisation?

A

Advantages:

  • No need to move to mate (common in sessile organisms)
  • Can produce many offspring

Disadvantages:

  • Reduced rates of fertilisation
  • Can only occur in aquatic environments
19
Q

What are the advantages and disadvantages of Internal Fertilisation?

A

Advantages:

  • Increases rates of fertilisation success
  • Can occur in terrestrial or aquatic environments

Disadvantages:

  • Need to locate a mate
  • Requires cooperative (often complex) behaviour
  • Requires specialised reproductive systems to transfer sperm from males to females
  • Fewer offspring produced
20
Q

What are the different modes of giving birth?

A

If internal fertilisation, need to “give birth”
» Oviparous: female lays zygotes as eggs
» Viviparous: embryo develops within mother’s body (generally fed by placenta, but in some species as eggs fed by yolk)

21
Q

What are Placental mammals?

A

Placenta feeds the developing embryo

» Exchange b/w maternal and embryo’s blood capillaries (nutrients in, waste out)

22
Q

What level of parental care is given to the offspring of externally reproductive organisms such as coral?

A

None – gametes released

23
Q

What level of parental care is given to the offspring of Oviparous organisms?

A

Some – guard fertilised eggs

24
Q

What level of parental care is given to the offspring of Viviparous organisms?

A

Extensive – protect & nurture until adulthood

25
Q

How is the sex of Mammals and some insects determined via chromosomes?

A

» XX/XY (most mammals, some insects)

• XY = male, XX = female: Y chromosome expresses male features (and inactivates X chromosome)

26
Q

How is the sex of some insects determined via chromosomes?

A

» XX/X0 (some insects)

• XX = female, X0 = male: Sex determined by amount of genes on X chromosome expressed

27
Q

How is the sex of birds, some reptiles, some insects determined via chromosomes?

A

» ZW (birds, some reptiles, some insects)

• More varied; usually ZZ = male and ZW = female

28
Q

How is the sex of other animals besides mammals, birds, some reptiles and some insects determined via chromosomes?

A
  • Others

• Platypus & echidna have 5 pairs of sex chromosomes (2014 study suggests 1 dominant Y chromosome)

29
Q

What is sex determination via the environment?

A

Where environmental factors influence the sex of an organism

30
Q

What is the main sex determining environmental factor and what animals does it affect?

A

Temperature-dependent sex determination
» Some reptiles, turtles and tuatara
» Impact of climate change?

31
Q

What is another sex determining environmental factor and what animals does it affect?

A

Social
» Sequential hermaphrodites
• Bluehead wrasse
• Clownfish

32
Q

What is another sex determining environmental factor and what animals does it affect?

A

Contact
» Marine worm larva develops into tiny male if it comes into contact with female (then sucked into genital sac of female, producing sperm and receiving food); otherwise develops into female

Biology (27 decks)

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