1. Reproductive strategies for Survival

2. How many, and how often? r Selection (aka. Quick-and-many)
K selection (aka. Slower and fewer)
Age of maturation
Young – usually before the next breeding season
Older – usually many seasons after birth
Number of offspring
Many
Few
Frequency of breeding
Usually frequently (many times a season) – high fecundity = many eggs produced per breeding season
Generally once a season. Low fecundity
Size of offspring
Usually small
Generally larger
Mortality rates
High – many offspring do not live to sexual maturity
Low – offspring generally survive
Examples of species
Mice, rabbits, most insects, cane toads, octopus, mass spawning organisms
Humpback whales, elephants, humans, some birds

3. Eggs or liveborn young? Oviparity Viviparity Literally means
Ovum = egg, parus = bearing
Vivus = living, parus = bearing
Description
Eggs released by mother, embryos develop outside mother’s body, nourished by egg yolk
Embryo develops in mother, born as young. Mode of nutrition varies
Benefits
Reduced energy use in care of young
Yolk provides good nutrient source
More likely for offspring to survive to birth
Drawbacks
Eggs may need to be incubated
Less chance of survival to birth due to eg. Eggs desiccating, predators, poor environment
Energy expenditure for female carrying offspring
Examples
Birds, sharks, reptiles, monotremes
Humans, some snake species, most mammals

4. Oviparity Bony fish and frogs Birds and reptiles Known as Shell-
Amniote eggs
Shell
None, or leathery membrane
Usually a hard, calcerious shell
Benefits
Wedge into safe crevices
Better protected from desiccation – do not have to reproduce in water
Dangers
Desiccation
Damage
Cannot be hidden in crevices
Examples
Port Jackson shark, amphibians
Hens, monotremes, crocodiles

5. Viviparity Egg yolk viviparity Placental viviparity
Types of viviparity are recognised by the nutrient source for the developing embryo
Egg yolk viviparity
Placental viviparity
Other source of nutrient
More notes
Cool habitat – kept warmer within body
Largish eggs
Any – nutrient sent via blood stream to embryo
Very small eggs
Feed them unfertilised eggs
Feed them “uterine milk” – secretion from uterus
Examples
Some sharks and snakes. Sea snakes – so that they do not have to return to land to breed
Mammals except monotremes, hammerhead shark
Porbeagle shark (feeds with eggs), Bat rays (feed with “milk”)

6. Activities
Glossary: r selection, K selection, fecundity, oviparity, viviparity, amniote, placenta, mortality, monotreme
Quick check questions: pg 383, 387.

7. Parental care or not? No parental care Care of laid eggs Care of young
What is it?
No contact with offspring after eggs are laid
Guarding and/or incubating eggs to hatching
Care of young after hatching/birth
Benefits
Free to mate more
No energy expenditure
Eggs have protection from predators/ harsh conditions
High chance of offspring survival
Drawbacks
High levels of mortality
Energy expenditure
Some mortality after hatching
Very high levels of energy expenditure – may not be able to mate for many years after offspring birth
Examples
Reef fish, frogs, turtles
Seahorse, diamond python, cephalopods (eg. Octopus, squid), spiders
Humans, primates. Mammals (milk), emperor penguins, emus

8. Case studies – 1. Australian Mallee Fowl
Male invests energy into nest building – incubation mound made of rotting plant matter
Female invests energy into laying 12 to 24 eggs at once
Male incubates
Chicks hatch, do not require further care

9. Case studies – 2. Emu Polyandrous Male is caregiver
He builds nest, incubates eggs, guards young
Female lays eggs and leaves to mate again

10. Case studies – 3. Australian Marsupials

11. Australian Marsupials
Placental mammals (not marsupials) have a long period of uterine development
In contrast, marsupials have a short period within the uterus, and a long period developing in the pouch
TURN TO PAGE 391 IN YOUR TEXT BOOK

12. Australian Marsupials – arrested development
Kangaroos and wallabies can suspend development within the uterus
If kangaroo conceives while young is in pouch, she stops uterine development until pouch young is off the nipple in the pouch.

13. Activities Glossary: cephalopod, marsupial, placental mammal
Quick check pg 393