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Terms in this set (26)
1) Life histories-The intrinsic (evolved) traits of a species that determine its broad patterns of birth, death, immigration, and emigration.
2) Environments-The extrinsic factors affecting a specific population of a species, such as resources, competitors, predators, catastrophes.
What are 2 reasons why vital rates vary?
Lifespan, Birth schedule (# of broods, # of offspring per brood, and maturation rate), Parental investment (offspring size and parental care), and Dispersal ability.
What 4 factors define life histories?
Low fecundity, low infant mortality. Extremely advanced parental care, abundant food, and very low "external" mortality. Modern humans, developed societies, dall sheep, and other mammals.
Describe a Type I survivorship curve. Give examples.
"Diagonal" Moderate fecundity, high early mortality. Some parental care. Birds, come mammals (including pre-industrial humans), some plants.
Describe a Type II survivorship curve. Give examples.
Very high fecundity, very high early mortality. No parental care. Oak trees, oysters, fecund fish, mushrooms.
Describe a Type III survivorship curve. Give examples.
Some sort of trade off. This often arises as survivorship vs. reproduction.
Most life history strategies in nature involve what?
It is best to invest time and energy in reproduction now or spent time and energy waiting to reproduce in the future? The constraints are: present reproduction subtracts energy available for future reproduction and the present is relatively certain and the future is uncertain.
What is the tradeoff between survivorship and reproduction? What are the constraints?
1) Semelparity-Reproduce once per lifetime (monocarpy in plants).
2) Iteroparity-Reproduce many times (polycarpy in plants).
3) Annual-Complete life history in a single year, reproduce than die (a special case of semelparity).
4) Perennial-Life history takes multiple years to complete (often implies iteroparity).
Describe the 4 different patterns of birth.
Semelparity-Favored when the probability of surviving to reproduce again is low and the amount you reproduce (fecundity) is lower later in life.
Iteroparity-Favored when the probability of surviving to reproduce again is high and later in life fecundity is also high.
When is semelparity favored? When is iteroparity favored?
Longer-lived species reproduce later.
How are survivorship and age at first reproduction related?
Organisms that produce fewer offspring invest more in each. Plants that produce larger seeds produce fewer.
How are brood size and parental investment related?
Refers to both the movement of individuals from their birth site to their breeding site, as well as the movement from one breeding site to another. Often small offspring are well-suited for dispersal. Dispersal can reduce competition among close relatives and allow colonization of new areas. Dispersal can allow escape from areas with diseases or high predation. However, an individual could end up somewhere worse unless dispersal is directed.
What is dispersal? Why is it favored in some species?
Leave as many offspring as possible in the next generation.
# of offspring per brood-Many
How to be the perfect organism:
Grasshopper (r selected)
# of offspring per brood-Many
What's an example of a species that "lives fast and dies young"?
Galapagos Giant Tortoise (K selected)
# of offspring per brood-Few
What's an example of a species that lives slow and dies old?
In a risky or temporary environment, investing in lifespan-enhancing traits may yield little reproductive return, since few individuals will actually survive. The solution to this is to make lots of small, "cheap" offspring that disperse far. A few may land in a good environment (e.g. freshly burned; lots of new growth) and hit the jackpot.
Why would any organism evolve to die young like the dandelion or grasshopper? Why be r-selected? How does this work for many organisms?
In a constant environment (desert island, old growth forest), populations are usually near its carrying capacity. Only the largest individuals will compete successfully. Investing in faster reproduction may yield low return. The solution is to invest in a large adult body size, and in fewer but higher-quality offspring (larger, better cared for).
Why be K-selected? Why not use all of that energy to make more babies?
1,000s of eggs or seeds, extremely high death rate, and fast dispersal. Populations fluctuate sharply with crashes and quick recoveries, rapid spread, includes many pests and weeds.
What are some consequences for population dynamics of being r-selected?
Few offspring, low death rate, adapted to "old-growth" (stale) habitat. Populations are more constant, declines may be hard to reverse, includes many endangered species!
What are some consequences for population dynamics of being K-selected?
Competitors-Low Stress (high resource availability) and low disturbance. (birch trees)
Stress Tolerators-High Stress (low resources) and low disturbance. (ivies)
Ruderals- Low Stress and high disturbance. (dandelions)
Know this triangle and this slide. Classify life history syndromes based on habitat (competitors, stores tolerators, and ruderals).
Where food resources are most abundant. The global population growth is not approaching food limitation yet.
Where is human population growth the lowest?
Populations of populations. Spatially isolated populations linked by dispersal of individuals or gametes. Some are sources and some are sinks.
What are meta populations?
Sources produce more emigrants than immigrants they receive.
Sinks have more immigrants than emigrants produced.
What are sources and sinks?
Each local population may go extinct, but the metapopulation persists due to dispersal and recolonization of habitat patches.
What are metapopulation dynamics?
r-selected species and many others. Sometimes, local populations disappear and reappear.
What kind of species show erratic population fluctuations?
Many habitat patches, even unoccupied ones, connectivity across the landscape
How can meta populations be preserved?
THIS SET IS OFTEN IN FOLDERS WITH...
1-Lectures 1 & 2
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