LE 5: Life History Flashcards
What are life history traits?
Characteristics of an organism that affects its survival and reproduction.
The life schedule of an organism maximizes fitness for a particular species.
How was growth and development in mammals developed over time?
Evolution of growth and development in mammals to birth more relatively developed offspring.
Monotreme/echnida (oldest form of mammals): undeveloped offspring
Maruspials (e.g. kangaroo): a bit underdeveloped
Eutherian/human: relatively developed
What are the 4 dimensions of life history?
Survivorship: how likely an organism is likely to survive after a certain age.
Fecundity: how many offspring are produced
Parental care: how much investment into the offspring is made
Age of Sexual maturity
What are the types of survivorship and how does it affect their life history?
Type I (humans and primates) die later in life, have low numbers of offspring, and need lots of parental care.
Type II (birds) die equally at each age mark, have less offspring, and provide moderate parental care.
Type III (trees, marine invertebrates, fish) do not survive early, have lots of offspring, and little parental care
What does each of the continuum of life history strategies mean?
r-selected: fast reproductive rate
in between
k-selected: caring capacity/ slow life history because they use a lot of resources to care for offspring
How does selection affect traits to adapt to the changing environment; magpie clutch size example?
Temperate region has more offspring. There is less parental investment because they leave the nest less often, which increases the survivability. More offspring but of lower quality; optimal if there are more predators.
Tropical regions have less offspring. There is more parental investment because they leave the nest more often to find resources, which decreases survivability. Less offspring, but of higher quality; optimal if there are less predators
How does the environment relate to fitness?
Seed dispersal example:
Dispersal propensity: proportion of seeds in a population that were the distal seed morph, based on all the fruits by a maternal plant.
There is higher dispersal when seeds are in the distal parts.
There are different dispersal strategies: some seeds have a pericarp, a spongy coating, that allows for them to float to another environment. Plants at mid-latitude means that there are larger distances to travel, resulting in larger pericarps (selected to increase fitness).
What is plasticity?
An organism’s ability to alter their physiology, morphology, or behavior in response to environmental conditions
What is parthenogenesis and how is it an example of plasticity?
Parthenogenesis is an optional reproductive strategy.
There are clones from germ cells that developing directly into an egg without going through meiosis.
There are genetically variable offspring where germ cells pass through only the first meiotic division and development continues afterward.
What are the tradeoffs of sexual recombination through parthenogenesis and regular sexual reproduction?
Sexual recombination, only half of the female’s genes are passed on with some genetic diversity by crossing over.
Regular sexual reproduction has more genetic diversity, which increases the chances of survivability of muations/diseases.
What is an example of parthenogenesis?
Aphids
Female aphis produce more females, resulting in clones. They produce males when conditions are crowded/stressful. They travel to a different environment to reproduce with the male, resulting in more genetic diversity.
How can external stimuli affect the life history trajectory? Give examples involving predation.
Red eyed tree frog eggs:
When they sense vibrations of predators, they hatch earlier in response. The tradeoff: smaller/low body mass which can lead to starvation because they have less energy to find needed resources.
Guppies:
When there is high predation risk, they grow to be smaller. There is a higher percentage of energy into offspring and more offspring that increases the survivability of offspring.
When there is low predation risk, they grow to be larger. There is a lower percentage of energy into offspring, resulting in less offspring.
How can external stimuli affect the life history trajectory? Give examples involving climate change.
Flowering earlier when there was not a warmer climate has negative effects. Pollinators are not around for them to reproduce.
How do veeries modify their life history strategy in years when hurricane more intense to increase fitness?
Veery birds are able to predict when there will be more intense hurricanes each year, which affects how they modify their life strategy.
Nesting earlier and terminating their breeding season earlier. It allows for offspring to develop enough to survive the bad hurricane seasons.
Produce more offspring. Chicks are of lower quality but this increases the odds of at least a few chicks surviving to reproduce later on in their lives.
Decreasing the amount of nests that they have offspring in. This allows for the offspring to be taken care of more, leading to better chances of the offspring surviving in the harsh conditions.
What is senescence and the hypotheses that support it?
The process of organisms living past their reproductive prime.
Grandmother hypothesis: ancestral females benefitted by retaining their strength even as fertility declined
significance:
1. assist daughters in caring for their children
2. daughter increases her daughter’s survivability
3. longer survival impacts indirect fitness
