A concise, bullet-pointed summary on Diversity of Reproductive Strategies. Covers strictly what you need to know for all tests and assessments (as dictated by the SAGS guidelines). Includes annotated diagrams and images to illustrate points mentioned, as well as additional research, helpful when un...
- Displays are performed by animals seeking to advertise their willingness to mate
Three functions of courtship:
1. Helps partners recognise whether a potential mate belongs to the correct species
- Mating wasted if a male mates with a female of different species, as eggs may not be fertilised,
the offspring may die young or the offspring may be infertile
2. Ensures that mating takes place when both the male and female are ready to mate
- Very important for animals that release their eggs and sperm into water, such as frogs
3. Allows males and females to find out about the health and strength of a possible mate
- Many females select a mate based on physical characteristics that show he will contribute good
genes to the offspring
- Therefore, energy she puts in to her offspring isn’t wasted
- Selection for a mate is called sexual selection
Types of Signals
Visual Signals:
- E.g. long-tailed widow-bird in the grasslands of South Africa
- Males grow long tail feathers and females measure his fitness by the length of his tail and its
symmetry
- The longer the tail and the more symmetrical, the more females the male will attract
Auditory Signals:
- E.g. male giant bull frogs
- Gather at a pond and the male’s call is a long, low ‘whoop’
- Females attracted to the sound, and appear at the breeding arena
Chemical Signals:
- E.g. female moths release pheromones into the air
- Male moths of the same species detect pheromones and this is what attracts them
Physical movements:
- E.g. scorpions do a courtship dance
- Male stands facing female with abdomens high in the air, moving about in circles
- Male seizes females pincers and they walk backwards and forwards
- Male places sperm packet on the ground and moves female into a position so that the sperm
packet enters her genital opening under her abdomen
Mating Systems
- Mating: the act of pairing a male and female for reproductive purposes during the breeding
season
Types of mating systems:
- Monogamous: having only one mate at a time
- Polygynous: having more than one mate
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, Chloë van Beukering Life Sciences Notes 2020
- Polyandrous: a pattern of mating in which a female animal has more than one male mate
- Promiscuous: characterised by many sexual relationships
Parental Care
- Parental care is a form of altruism (self-sacrifice) since this type of behaviour involves increasing
the fitness of the offspring at the expense of the parents
- e.g. wild dogs
- The female has a litter of 2 to 20 pups, which are cared for by the entire pack
- Pups live in the den for the first 3 months of their life
- Mother is confined to the den while nursing and she relies on other pack members to feed
her during that time
- Packs have been known to share food and to assist weak or ill members
- Some members ‘baby sit’ the pups and chase predators away from the den
- Cannot successfully rear pups without assistance
- Appears that more pups survive in packs where there are more helpers to assist with their
care, but this is not always the case
Internal Fertilisation
- The sperm cell from the male is transferred into the female by copulation (sexual intercourse)
- The sperm cell then fuses with the egg cell inside the body of the female
- e.g. terrestrial mammals, birds and insects
- Specific e.g. Galapagos tortoise
- Advantages:
- Ensures that the sperm cell comes into contact with an egg
- Protected from predators
- Removed from harsh environments
- Disadvantages:
- Fewer eggs are produced
- The animal must have an organ to insert the sperm cells
External Fertilisation
- The sperm cell fuses with the egg cell outside the body of the female
- The sperm cells are discharged directly into water
- E.g. aquatic animals like frogs, sponges, jellyfish, worms and fish
- Advantages:
- No additional energy is needed for parental care or formation of a protective layer
- No need for a male to have a special organ to insert the sperm into the female’s body
- Chances of fertilisation are enhanced by courtship display by fish
- Does not need much energy
- Disadvantages:
- Chances are very slim for a sperm cell to meet the egg of same species
Types of Reproduction
3 types:
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