Covers the entire section on Reproductive Animal Strategies. Includes notes from the textbook, as well as additional class, video and research information, diagrams and practice questions.
Applicable to all IEB Grade 12s.
Written by a 90% < student.
Reproductive animal strategies
Reproduction = The production of a new generation of organisms from an existing generation.
Reproductive effort = To produce the maximum number of surviving offspring while using the
Reproductive effort = least amount of energy.
Reproductive strategies have developed to ensure maximum reproductive success in different
environments.
This enables species to breed successfully and then survive to a reproductive age.
Types of strategies:
A. Courtship
B. External vs internal fertilization
C. Ovipary, Ovovivipary and vivipary
D. Amniotic egg
E. Precocial vs altricial development
F. Parental care
, Type 1: Courtship
= Behaviour and/or signals that are designed to attract another animal for mating or breeding
Humans do not partake in this type of natural selection.
This makes a population successful as only the best genes are passed on.
Different forms:
1. Simple strategies
Includes: chemical (pheromones), visual (brightly coloured body parts) and auditory stimuli
e.g. Female moths produce species-specific pheromones that guide males towards them.
e.g. Most frogs have to return to the water for mating and breeding. Once male frogs reach the
breeding ground they sing or grunt or croak a species-specific sound to attract females.
e.g. Male birds advertise when they are ready to mate by singing a species-specific song that
attracts the female. When they meet the male must then impress and stimulate the female by
special plumage. (their feathers)
2. Complex strategies
Unique to each species.
The females usually favour the males that are larger, have more elaborate physical features and
display more energy in courtship.
This helps the females to choose the better male, which can reinforce a bonding pair and
promises healthier offspring.
e.g. Certain bird species, such as the blue crane’s courtship displays include a complex and
extended series of calls and elaborate dances by the male.
e.g. Springbok have an annual rut (a period of sexual excitement), usually when the animals are
in peak condition. To attract the females, males defend territory with loud grunts, attack
vegetation with their horns and deposit middens of urine and dung in a ritualised display.
e.g. Some bird species, such as the male African hoopoes, exhibit courtship feeding and feed
insects to their mate – allowing the female to save her energy.
How will courtship maximize reproduction?
- Ensures that males and females find suitable mates.
- Is times 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.
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