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Life Science study notes. Notes taken from the textbook Mind Action Series Life Sciences Grade 12
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Reproductive Animals Strategies:Reproduction is the production of a new generation of organisms from an existing
generation. Life process that ensures the continued survival of a species.
What is the goal of a species?
1. Produce maximum number of surviving offspring while using the least amount
of energy reproductive effort.
2. Breed successfully and survive to reproductive age.
This is done with strategies.
Strategy is a genetically determined behaviour.
Reproductive Strategies include:
A. Courtship
B. External versus internal fertilisation
C. Ovipary, ovovivipary and vivipary
D. Amniotic egg
E. Parental care
A. Courtship:
Courtship in animals is behaviour and/or signals that are designed to attract another
animal for mating and breeding.
What are the different forms of courtship?
1. Simple Strategies:
* Such as chemical (pheromones), visual (brightly coloured body parts) or
auditory stimuli are used for mates to find each other; they can be used
singly or in a combination
* For example:
- Females of some insect species, e.g. moths produce species-specific
pheromones that guide males towards them.
- Most frogs have to return to water for mating and breeding. Males then sing
(croak) to attract males.
- Male birds advertise when they are ready to mate by singing a species-specific
song that attracts the females.
2. Complex Strategies:
* Unique to each species.
* Females usually favour males that are:
1. larger
2. Have more elaborate physical features
3. display more energy in courtship activity than other males.
, * This helps female to choose the better male, which can reinforce pair bonding
(important for parental care) and promises healthier offspring (more will
survive).
* For example:
- Certain bird species have complex courtship patters, e.g. Blue Cranes’
courtship displays include:
+ a complex and extended series of calls
+ elaborate dances by the males
- Springbok have an annual rut (a period of sexual excitement), usually when the
animals are in peak condition. To attract females, males defend territories with
loud grunts, attack vegetation with their horns and deposit middens of urine and
dung in a ritualised display.
- Some bird species exhibit courtship-feeding, e.g. male African hoopoes feed
insects to their mates – allow female to save energy for incubating and
brooding.
How will courtship maximise reproduction?
Courtship mechanisms ensure that males and females find suitable mates,
e.g. the strongest male.
Sexual behaviour in courtship is timed so that the male and female are ready
for mating at the same time.
Energy expenditure is usually by the male, the female conserves her energy
for breeding.
B. External versus internal fertilisation;
Fertilisation is the joining of the nucleus of an egg and a sperm.
1. External Fertilisation:
External fertilisation takes place in water and occurs in most aquatic
vertebrates, e.g. fish and frogs.
It is wasteful as huge numbers of eggs are produced, and most are
eaten
Fertilisation is not certain here.
How can external fertilisation maximise reproduction?
Huge numbers of eggs and sperms are released into the water.
Courtship rituals can take place, e.g. many fish swim side by side when
releasing their eggs and sperm which ensure that male and female
gametes are close together.
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