2.4 Sex and Behaviour Flashcards
(28 cards)
What is parental investment?
Can be defined as resource usage by a parent to benefit future or existing offspring
Compare gamete production between males and females?
A human male can release around 300-500 million sperm cells in a single ejaculation, while a human female will release around 450 mature eggs in a lifetime
Why are eggs larger than sperm?
The egg contains a large food store that provides energy to support the developing zygote until it can feed from the placenta
What do selection pressures favour in terms of human gametes?
Favours larger eggs as they contain a larger food store, and favours sperm with no excess mass to ensure they are fast moving
What are r-selected and K-selected organisms?
Organisms can be classed due to the degree of parental investment in offspring and the number of offspring produced,
What is an example of an r-selected organism?
Oyster, they produce 500 million offspring a year and have very little parental investment
What is an example of a K-selected organism?
Chimpanzee, they have 1 offspring every 5 years and have a much higher level of parental investment
What is internal fertilisation?
The process by which the sperm and the egg nuclei fuse inside the female
What are costs of internal fertilisation?
Mate must be located- high energy use,
Requires direct transfer gametes
What are benefits of internal fertilisation?
Increased chance of fertilisation,
Fewer eggs needed,
Allows for development and protection,
Higher offspring survival rate
What is external fertilisation?
Male and female gamete nuclei fuse outside the female
What are costs of external fertilisation?
Gamete predation is high,
Chances of fertilisation is low,
Few offspring survive
What are benefits of external fertilisation?
Very large number of offspring can be produced
What is monogamy?
A pair of animals mates to the exclusion of all others
What is polygamy?
Individuals of one sex having more than one mate, it can be subdivided into polygyny and polyandry
What is polygyny?
One male mates exclusively with a group of females
What is polyandry?
One female mates with a number of males in the same breeding season
What is a courtship?
A specialised behaviour that attracts a member of the opposite sex and leads to mating
What are courtship rituals?
Signals that only the others of the same species understand, e.g. giving off chemicals, making sounds or displays
Why do courtship rituals increase the chance of successful reproduction?
Individuals mate when most fertile
What is a fixed action pattern?
An instinctive behavioural sequence that is relatively consistent within the species. They are a series of sign stimuli followed by responses
What is a sign stimulus?
A trigger which provokes a specific innate behavioural response in an animal. This could be a production of a chemical or making displays
What is reversed sexual dimorphism?
The normally inconspicuous female is larger or more ornate than the male
What do females assess in male courtship and appearance?
Honest signals of fitness which allows them to choose healthier males to increase their own fitness and reproductive success
