2.4 sex and behaviour Flashcards
Parental investment definition
Any time or energy invested to benefit their offspring.
Parental investment detriment to parents
Looking after existing offspring
Continuing to reproduce
Lose out on their own well-being and survival
When does parental investment occur
Where the benefits to the species outweigh the cost.
Sperm and egg parental investment
Male members of a species invest in producing as many sperm as possible to fertilise the egg, however female members produce far fewer egg cells and invest in providing nutrients for developing offspring.
Factors determining parental investment
Number of offspring produced
Environmental stability
Advantages of parental investment
Lower risk of young being predated
Increased size of offspring due to more successful parental hunting.
Low mortality rate in parental investment
Where a species produces very small numbers of eggs and undergoes intensive parental investment
K selected species
Larger and live longer
Mature slowly
Can reproduce many times in lifetime
Produce few larger offspring
High level of parental care
High survival rate of offspring
Selection tends to occur in stable environments.
Internal fertilisation
Where the sperm and egg nuclei fuse inside the female
High mortality rate
Where many eggs are produced but there is a low amount of parental investment and therefore many offspring die.
External fertilisation
Where the egg and sperm fuse outside the female typically in water
R selected species
Smaller and shorter lifespan
Faster generation time
Mature rapidly
Reproduce earlier and usually only once
Produce large quantities of offspring
Limited parental care
Most offspring don’t reach adulthood
Unstable environments selected for.
Courtship behaviour in external fertilisation
Individuals will signal to individuals of the opposite gender when their eggs are ready to be fertilised.
Water necessity in external fertilisation
External water prevents gametes drying out and allows sperm to swim through medium
Internal fertilisation requirements
Highly advanced reproductive systems
Cooperative behaviour
Copulation
External fertilisation requirement
Water
External stimuli and courtship behaviours
Environmental stimuli
Where environmental factors such as light intensity cause a species to undergo specific mating behaviours.
Advantages of external fertilisation
Larger amount of offspring produced
Less parental investment needed so parents aren’t detrimentally effected.
Advantages of internal fertilisation
Can occur when there is no external moisture
Higher success rate of offspring
More parental investment
Disadvantages if external fertilisation
Many gametes predated or not fertilised
Few offspring survive
No or limited parental investment.
Internal fertilisation disadvantages
Mates need to be located which requires large amounts of energy
Requires direct transfer of gametes from one organism to another.
Monogamy
Where one female and male will mate for life
Polygamy
Where one individual of a species will mare with many individuals of opposite sex.
Polygyny
Where one male mates with many females of the same species
Polyandry
Where one female mates with many males of the same species.
Monogamy reason
Can provide high levels of parental care to the offspring giving them a better chance of survival.
Polygyny reason
To allow the highest fitness individuals to pass their genes on to the next generation.
Polyandry reason
To allow for increased variation in a species and allow the species to become better adapted to selection pressures.
Sexual dimorphism
Where a male and female individuals in a species have different physical characteristics.
Examples of traditional sexual dimorphism
Males are larger and have longer teeth in baboons
Male birds have bright coloured feathers to attract females.
Reversed sexual dimorphism
Where female individuals in a species are larger and display characteristics that males would display in traditional sexual dimorphism.
Examples of reversed sexual dimorphism
Angler fish
Some bat species.
How does sexual dimorphism occur
By females sexually selecting the males with largest size and best weaponry - which will progressively be increased as these characteristics in males are passed onto the next generation.
Characteristics which help in male male rivalries
Size
Weaponry
Sneakers
Size in male male rivalries
Can help an individual outfight rivals of the same species
Weaponry in male male rivalry
Can help an individual outfight rivals of the same species
Sneakers in male male rivalry
Males impersonate a female and then mate with other females whilst males are competing with each other.
Species specific stimuli
Features in a species which cause a fixed action response - for example the presence of the opposite sex or ultrasonic signals of bats
Fixed action responses
An instinctive behaviour which a triggered by a species specific stimuli
For example mating dances and moths dropping to the floor.
Female choices factors during sexual selection
Physical appearances - good genes
Chemical signals - good genes
Presence or absence of parasites - health
Lekking species
Where a species uses allocated communal areas to provide an area to perform courtship displays. Ranging almost no interaction to cooperative dancing. This will allow for females to sexually select males of highest fitness.
Males and females will mate but don’t form long term bonds.
Advantages of lekking
Provides an opportunity for females to assess the males for high fitness traits
Reduce risk of predation whilst searching for mates
Increase chance of encountering individuals of the opposite sex.
