Reproductive strategies for survival

1
Chapter 12

• Reproductive strategies for survival

2
Key knowledge

• This chapter is designed to enable you to
• extend your knowledge of the variety of
  reproductive strategies in plants and animals
• develop an understanding of how various
  strategies assist successful reproduction in
  particular environments

3
At sea

• Read pages 374-376
• Create a table to summarise the similarities/
  differences and advantages/disadvantages between
• broadcast spawning and
• demersal spawning
• Answer quick-check questions 1-3 on p376.

4
A range of strategies

• type of reproduction (sexual/asexual)
• gender system (separate males and
  females/hermaphrodite/parthanogenesis)
• mode of fertilisation (internal/external)
• mating system (monogamy/polygamy/promiscuity)
• numbers of offspring (r-selected/K-selected)
• place of development/nutrition source for embryo
  (ovipary/vivipary)
• investment of parental care into offspring

5
Mating systems

• Monogamy one male and one female, may be just
  for a breeding season, or for life.
• Polygamy two types
• polygyny one male has multiple female partners
  during a breeding season and usually live in the
  area
• polyandry one female has multiple male partners
  during a breeding season and usually live in the
  area
• Promiscuous mating systems many males and many
  females mating in a breeding season
• Provide examples for each type of mating system

6
Offspring

• Two main strategies for animals
• 1. r-selected quick and many high fecundity
• animals generally reach sexual maturity very
  quickly, produce large numbers of offspring and
  breed frequently
• offer little to no parental care
• Provide three examples of r-selected animals
• 2. K-selected slower and fewer
• animals generally mature slowly and produce fewer
  and larger offspring
• Most put extensive parental care into rearing
  their offspring
• Provide three examples of K-selected animals

7
Offspring

• For plants
• shorter-lived annual plants often produce large
  numbers of tiny seeds
• longer-lived plants generally much larger seeds
  with food reserves for the developing embryo
• Answer quick-check questions 4 5 on p381

8
Eggs or liveborn

• Ovipary
• Eggs are released by the mother meaning they
  develop outside the body
• The nutrients for growth come from the yolk in
  the egg
• The eggs of birds and reptiles are called amniote
  eggs. The features include
• a protective outer shell
• a series of inner membranes (amnion, allantios
  and yolk sac)
• Larger eggs require more energy so animals that
  lay larger eggs lay fewer eggs.
• There are several advantages and disadvantages to
  laying eggs. Discuss these.

9
Eggs or liveborn

• Vivipary
• embryo develops within the body of the mother
• nutrition can occur in three different ways
• Egg yolk vivipary (some sharks and snakes)
• eggs are laid and stored internally for
  protection
• embryos nourished by the yolk of the egg only
• 2) Placental vivipary (all mammals except
  monotremes)
• nutrients delivered from the maternal bloodstream
  via placenta
• embryo enclosed within a fluid-filled sac,
  develops in the uterus
• 3) Other sources (some sharks and rays)
• read through strategies on p386-387
• Answer quick-check questions 9-13 p387

10
Parental care

• Leaving the eggs unprotected
• turtles lay their eggs in nests on the beach and
  do not attend to them
• Caring for eggs after laying
• some animals that lay eggs protect them until
  they hatch
• e.g. male seahorses, most birds, some cephalopods
• Parental care of young
• many animals provide protective care for their
  young
• Read and explain the following two examples
• Example 1 The Emperor penguin p389
• Example 2 The Australian mallee fowl p390

11
Australian animals marsupials

• Australia and South America have a special type
  of mammal called a Marsupial mammal.
• Features of marsupial reproduction
• very brief development in the uterus, resulting
  in immature stage of development when born
• after birth, the embryo makes their way through
  the fur from the vagina to the pouch
• embryo attaches themselves to the teat in the
  pouch where development continues
• Kangaroos, wallabies, koalas and wombats are all
  examples of marsupial mammals.
• Answer quick-check questions 14-17 on p393

12
Breeding patterns

• The breeding season is when mature members of an
  animal population have sperm and egg ready for
  release and fertilisation.
• The breeding season has two different names
  depending on the mode of fertilisation
• internal fertilisation mating season
• external fertilisation spawning season
• Males of many species continually produce sperm,
  whereas females produce eggs in a period called
  the oestrus cycle.
• Oestrus cycles follow a pattern based on the
  species.
• Provide examples of three different animals and
  their oestrus cycles.

13
Breeding patterns

• Some animals only mate once in their life time,
  after they mate, they die.
• Using the example of one of the animals on
  p394-395, explain this breeding behavior.
• Answer quick-check questions 18-20 on p395.

14
Plant reproduction

• Plants obviously do not mate, but they still need
  to reproduce.
• The means by which pollen is transferred from the
  pistil to the egg in the ovary is termed
  pollination.
• Plants have evolved strategies to ensure
  pollination occurs.
• There are two main ways this can occur
• blown by the wind, or
• carried by animals (birds, bees, bats, possums
  etc).

15
Wind pollination

• The pollen of all conifers and some flowering
  plants (e.g. grasses and some trees) is carried
  by the wind.
• Pollen that is carried by the wind is small,
  smooth and light.
• Flowering plants that are wind pollinated
• are not obviously brightly coloured (why not?)
• have their stamens exposed to the wind
• have feathery stigmas that can catch passing
  pollen grains

16
Animal pollination

• Most flowering plants are pollinated by insects,
  birds or other small animals.
• These animals are called vectors.
• These animals are attracted to the plant by the
  sugary reward they receive, nectar.
• When the animal comes to feed on the nectar, they
  get a bit of pollen on them. When they move to
  the next plant to feed, they inadvertently
  transfer this pollen to other plants.
• These plants have different features depending on
  the vector.

17
Animal pollination
Insect pollinated flowers Bird pollinated flowers
typically blue, purple or yellow in colour may have a shape that includes a platform for the insect to land - - - - - - - - - - -
Complete the table above using p396-398 of the
textbook.
18
Dispersing plant offspring

• In flowering plants and conifers, the embryo that
  results from fertilisation of the egg by pollen
  is enclosed in a seed.
• This seed needs to be transported to other
  locations for dispersal, which can occur a number
  of ways
• sailing in the wind
• drifting on water currents
• hitchiking on animals
• hitchiking inside animals
• Explain the above four methods of seed transfer,
  using examples.
• Answer questions 21-25 on p400.

19
Chapter Revision

• Answer Biochallenge questions p401
• Answer the following chapter review questions
  p402-404
• 2, 3, 4, 5, 8 and 10