Unit 2 - Sex and Behaviour Flashcards
Parental investment
The use of resources by a parent to benefit future or existing offspring.
Benefits - increased number of offspring surviving, which increases the evolutionary fitness of the parent.
Gamete production
Initial parental investment in gametes is unequal.
Male - sperm need to be small and fast moving, so selection pressure reduces their mass. Large numbers of sperm are produced.
Female - selection favours larger eggs with a bigger energy store. Fewer are produced.
Investment in reproductive structures
There is greater investment by the female in gametes, and in the uterus and gestation (in mammals).
External fertilisation
Gametes are released into the environment (water). eg. amphibians, fish, coral.
Chances of fertilisation are low, so many gametes are produced.
No parental care, few survive so large numbers are produced.
Internal fertilisation
Gametes are released into the reproductive tract of the female. eg. mammals, birds
There are energy costs in finding a mate and transferring gametes between partners.
Fewer eggs are needed as chances of fertilistaion are high.
Offspring develop internally so are more likely to survive.
R-selected species
Small species.
Short generation time
Reproduce early and often only once.
Produce many small offspring which receive a low energy input and limited parental care.
Strategy used by opportunistic species in unstable environments.
K-selected species
Longer lived and slow to mature.
Reproduce many times in a lifetime.
Produce few, larger offspring with a high level of parental care.
Offspring are more likely to survive to adulthood.
Experience strong intra-specific competition for resources in stable environments.
Mating systems
How many mates an animal has in one breeding season.
Polygamy
Individuals of one sex have more than one mate.
Polygyny - one male mates exclusively with a group of females.
Polyandry - One female mates with a number of males in the same breeding season.
Monogamy
Each individual only shares gametes with one other individual to the exclusion of all others. eg. Schistosoma parasite
Courtship
Courtship involves behaviours and characteristics associated with mate selection.
DNA sequences that increase chances of successful breeding are favoured by sexual selection.
These sequences are not favoured by natural selection, as they do not improve survival chances, but they do improve chances of successful reproduction.
This leads to an overall increase in evolutionary fitness.
Ritualised courtship behaviours
A specific sign stimulus from one individual produces a fixed-action response pattern in the other.
This is instinctive, and varies little between individuals of the same species.
eg. in sticklebacks, the swollen belly of the female acts as a sign stimulus for the male to commence a zig-zag courtship dance.
Imprinting and courtship
Mate choice can be influenced by sexual imprinting early in life.
Imprinting is an irreversible developmental process that occurs during a critical time period in young animals.
Imprinting increases fitness, as forming a strong attachment to a parent improves survival chances.
Imprinting affects mate choice as offspring select mates that resemble parental phenotypes.
Lekking
Communal displays by groups of males.
Females visit the area to select suitable mates.
Territorial dominant males fight each other for the best positions in the centre of the lek.
Alternative male strategies
Sub-ordinates and juveniles are pushed to the edges, and are known as satellite males. They are smaller, and are tolerated by dominant males as they attract more females to the lek. They attempt to intercept the females before they reach the centre of the lek.
Sneaker males are the same size as females and have the same plumage, so they are not spotted by dominant males..
