Life histories Flashcards
Describe the life history of the Magicada sp (Hemiptera insecta)
Lays lots of eggs, nymphs live underground for up to 17 years before coming to the surface as an adult to breed
Decribe the life history of the Sequoiadendron giganteum (conifer tree)
live for up to 3000 years, most of life spent as adult (reproduce from 12y/o), produce many seeds each year
Define life history
the significant features of the life cycle through which an organisms passes, with particular reference to strategies influencing survival and reproduction
Give the life history theory
the theory that many physiological and behavioural traits can be understood in the context of the major characteristics that define the life history of the individuals
Define extrinsic factors
environmental factors
Define intrinsic factors
genetic factors as a result of trade-offs
What are the 2 main categories of life history strategies of plants and animals
Semelparity and iteroparity
Describe semelparity life histories
Organisms gather lots of resources for 1 large reproductive event
Describe iteroparity
More than one reproductive event (seasonal breeders)
Describe a trade off between traits
body size and generation time (larger body size = longer generation time)
Describe the relationship between brood size and survival
Increasing litter/parental care, survival of parents decreases (shows how expensive reproduction is)
What is the fast-slow continuum?
Index of life histories in relation to body mass showing that larger mammals have longer life cycles than smaller mammals
Why do bats have faster life cycles than expected?
they share many traits with birds
Why do primates (e.g. humans) have slower life cycles than expected
bigger brain takes a longer time to develop
Give the 3 mating systems
monogamy (most present in birds), promiscuity and polygamous
What are the 2 forms of polygamy
polygyny - 1 male + multiple females (e.g. lions)
polyandy - 1 female + multiple males
Briefly describe how monogamy developed in birds
Reptile ancestor is promiscuious with female-only care. females start to invest more in larger eggs, which required surface incubation. Female becomes more choosy, causing development of courtship and eventually monogamy
Why is monogamy more common in birds than mammals?
eggs can be incubated by both males and females, so joint parental roles is more possible
What are the 2 preconditions for the evolution of polygamy
- multiple mate/sufficient resources to attract multiple mates that must be energetically defensible by individuals
- the ability of animals to use this potential
Give a benefit of polygamy
one sex is free from parental care so can concentrate on territorial defence etc
Describe the varying parental cares of different mating systems
monogamy - bi-parental
polygyny - female-only
polyadry - male-only
promiscuity - no postnatal care
Under which conditions is parental care favoured?
a predictable OR stressful environment, and with distance/scattered food
Describe 3 potential reasons for a higher clutch size at higher latitudes
- longer springs in temperate regions allow for more food availabiilty
- clutch size directly proportional to seasonal variations in resources (unpredictable conditions in temperate regions favours a larger clutch size for higher chance of survival)
- larger clutch size to take advantage of beneficial environmental conditions (less competition in spring due to higher mortality in winter)
what do r and k mean in terms of population ecology?
r = intrinsic rate of natural increase k = carrying capacity
Describe an r-selected individual
r-selected individuals have been selected for their ability to reproduce rapidly (present in unpredictable environments)
- small size
- earlier maturity
- semelparity
- lots of small offspring
Describe a k-selected individual
k-selected individuals have been selected for their ability to contribute towards populations near to the carrying capacity (present in populations of high competition)
- larger size
- deferred reproduction
- iteroparity
- few, large offspring
