This is a summary of the whole Reproductive Animal Strategies chapter in the Life Sciences Mind Action Series Grade 12 IEB textbook.
The work is summarised in detail, and then very brief summaries are also included at the end.
Diagrams, images and a definitions column is included in order to...
GOAL OF EACH SPECIES DEFINITIONS:
- To produce the maximum number of surviving offspring while REPRODUCTION
using the – production
of a new generation of
least amount of energy (this is called the reproductive effort).
organisms from an existing
- Asexual reproduction is energy efficient, whereas sexual reproduction
generation.
needs a much higher energy input.
- Unique reproductive strategies have enabled the species to breed
FERTILISATION – joining of the
successfully and then survive to reproductive age. nucleus of an egg and a sperm.
A. COURTSHIP
Behaviour and/or signals that are designed to attract another animal for mating
and breeding.
Different forms of courtship:
- Simple strategies
o Chemical, visual, or auditory stimuli used for mates to find each other.
o Example – When male frogs reach the breading ground, they sing to attract females.
- Complex strategies
o Unique to each species
o Females usually favour the males that are:
▪ Larger
▪ Have more elaborate physical features
▪ Display more energy in courtship activity
o Example – Blue Cranes’ courtship display which is a elaborate dance by the males.
How well it will maximise reproduction:
- Ensure that males and females find suitable mates.
- So that males and females are ready for mating at the same time.
- Energy expenditure is usually by the male, the female conserves her energy for breeding.
Due to these factors, it is more likely that a strong healthy offspring will be produced.
B. EXTERNAL VS INTERNAL FERTILISATION
, Summary by: Kaylin Teneal
External fertilisation
- Takes place in water and occurs in most aquatic vertebrates
- Not an ideal process as:
o Wasteful as most eggs are eaten, and huge number of eggs are produced.
o Fertilisation is not certain.
- How it can maximise reproduction:
o Huge number of eggs and sperm are released into the water.
o Courtship rituals ensure the female and male gametes are near each other.
- Example – frogs release their eggs into a pond, most are lost due to predation.
Internal fertilisation
- Occurs in terrestrial invertebrates DEFINITIONS:
CLOACA – a single opening
- Most birds and reptiles mate using a cloaca, they line up their cloacae
located in the lower abdomen.
for the transfer of sperm.
- Males of virtually all mammals have a penis to introduce the sperm into
the female (process is called copulation).
- How does it maximise reproduction:
o Fertilisation is more certain as the gametes are placed as
close together as possible.
o Don’t ensure fertilisation but makes it more likely.
o Energy is saved in producing fewer gametes can be used for
other purposes to maximise reproduction.
- Example – dogs/horses
C. OVIPARY, OVOVIVIPARY AND VIVPARY
Terms for reproductive strategies that describe the moment at which the future offspring separates
from a parent.
Ovipary (oviparous – egg producing then released)
- Egg develops inside parent
- Egg yolk is the only food that the developing embryos receive until they hatch from egg.
- Does ovipary in aquatic environments maximise reproduction:
o The eggs are very vulnerable to predation
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