Reproductive Strategies

Question 1

What is external fertilisation?

Answer 1

When gametes such as sperm and eggs are released and fuse outside the body

Question 2

What are the methods to increase probability of fertilisation?

Answer 2

• Release high number of eggs
• Releasing gametes in large groups
• Synchronize gamete release at the same time (may be hormone triggered)
• Salmon make redds to keep eggs in one spot for fertilisation
• Shrimp attach spermatocysts

Question 3

What is internal fertilisation

Answer 3

When gametes such as sperm and eggs fuse inside the body of a parent

Question 4

What does viviparity consist of?

Answer 4

• Internal fertilisation
• Internal and complete gestation (via placenta)
• Birth to live fully functioning young

Question 5

What does oviparity consist of?

Answer 5

• Internal fertilisation

- Fertilised eggs are laid and protected by the mother

Question 6

What does ovoviviparity consist of

Answer 6

• Internal fertilisation
• Eggs carried by the mother and hatch internally
• Live young released after eggs hatch

Question 7

What is a r-strategy?

Answer 7

an organism that produces large numbers of offspring while providing little parental investment

Question 8

What is a k-strategy?

Answer 8

an organism that produces few offspring but provides a large amount of parental investment

Question 9

Explain the tuna

Answer 9

• r-strategists
• Fecundity of up to 25 million
• No parental care - larvae to develop in planktonic environment

Question 10

Explain the whales

Answer 10

• k-strategists
• Viviparity - complete internal fertilisation and gestation via placenta
• Only 1 offspring with a long gestation period 10-16 months
• 4-11 month anti-natal care with milk from mammary glands
• “Family groups/pods” will help care for young until sexual maturity (2-5 years)

Question 11

Explain the sharks

Answer 11

• Generally considered k-strategists

- Employ methods of viviparity, ovoviviparity and oviparity

Question 12

Explain oviparity sharks

Answer 12

some sharks lay a “mermaid’s purse” and attach them to rocks or seaweed They will guard the eggs until hatched

Question 13

Explain ovoviviparity sharks

Answer 13

after hatching inside the mother, they can develop and grow stronger

Question 14

What do thresher and porbeagle juveniles do?

Answer 14

will eat unfertilised eggs (oophagy)

Question 15

What do sandtiger and nurse sharks do?

Answer 15

will cannibalize their siblings (embryophagy or intrauterine cannibalism)

Question 16

Explain viviparity sharks

Answer 16

hammerheads and bull sharks develop young internally as the egg yolk attaches to the uterus and forms a placenta