2.4
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what is parental investment
the energy, time, and resources parents devote to offspring, increasing survival but at a cost
why do females typically invest more than males
pregnancy, gestation, egg production, and limited gametes make female investment higher
why are sperm considered cheap
they are produced continuously in huge numbers and require little energy
why are eggs considered expensive
they are limited energy-intensive to produce and only available for part of the females life
what is internal fertilisation
sperm and egg nuclei fuse inside the female
what is external fertilisation
sperm and egg nuclei fuse outside the female, common in fish
what are the advantages and disadvantages of external fertilisation
benefits- very large numbers of offspring can be produced costs- many gametes are predated or not fertilised - no, or limited parental care - low offspring survival rate
what are the advantages and disadvantages of internal fertilisation
benefits- increased chance of successful fertilisation - fewer eggs required - offspring can be retained internally for protection and development - high offspring survival rate costs- a mate must be located, requiring energy expenditure - requires direct transfer of gametes from one partner to another
organisms can be classified into r-strategists and K-strategists based on…
…the level of parental investment in offspring and the number of offspring produced
what characterises r-selected species (quick and many)
small size, fast maturity, reproduces early in life often only once, large number of smaller offspring, limited parental care- most offspring don’t reach adulthood
what characterises K-selected species (slower and fewer)
larger size, longer lifespan, mature slower, reproduce many times, fewer offspring, high level of parental care- more offspring survive to adulthood
what type of environment favours r-selection
unstable environments with many available niches
what type of environment favours K-selection
stable environments
what is monogamy
one male and one female mate exclusively during a breeding season
what is polygamy
individuals of one sex mate with multiple partners
what are the names of the two forms of polygamy
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
successful courtship behaviour in birds and fish can be a result of…
species-specific sign stimuli and fixed action pattern responses (instinctive reactions)
what are species-specific sign stimuli
signals that trigger instinctive responses
what is a fixed action pattern
an instinctive, automatic behavioural response to a sign stimulus
what is sexual selection
selection for characteristics that have little survival benefit for the individual but increase chances of mating
what can be a product of sexual selection
sexual dimorphism- reversed sexual dimorphism exists in some species
what is male-male rivalry
competition between males for dominance and access to females, through real or ritualised fights using elaborate ‘weapons’ such as antlers, tusks or horns