Population Ecology Flashcards
What is population ecology?
looks at entire populations of a given species
Why are isolated populations at a greater risk of extinction?
Less gene flow, not enough variants
Are all 7 billion plus humans a part of one big population?
Yes, with the exception of Amazonian tribes.
To predict future growth or decline of a population what changes do we monitor? What are they useful for?
- density (ind/km ^2)
- distribution of individuals
- sex ratio (males: females)
- age structure
- birth and death rates
useful for assessing conservation means and human population growth
Population density
number of individuals in a population per unit area (individuals / km ^2)
What is a survivorship curve and what are the types?
when animals are most likely to die ,(birth and death rates depicted as curves)
- Type 1 = humans (higher chance of dying in elder years)
- Type 2 = many birds (equally likely to die throughout lives)
- Type 3 = trees, amphibians, insects (produce a ton of offspring and most don’t make it)
For the GRAPH , the x axis is AGE, the Y axis is SURVIVORS
Population growth rate
change in population size per unit of time
exponential growth rarely lasts long due to limiting factors (bio, chemical, physical attributes of env) (e.g., collard dove in Great Britain with unregulated population, and bacteria colonizing a dead animal)
carrying capacity
max population size of a species that env can sustain
Limiting factors prevent overshooting. Diebacks become stronger if population overshoots.
Humans can introduce predators into the environment to prevent overshooting, or they can maintain ecological balance by NOT KILLING the predators to begin with.
If population overshoots carrying capacity what happens?
dieback as effects of limiting factors become stronger
What factors affect population regulation?
- 50% comes from limiting factors from environment
- other 50% comes from attributes of the organism itself (high biotic and low biotic potential, fish laying thousands of eggs is high, a whale with long gestation is low)
What are the different reproductive species strategies?
r selected: produce as many offspring as possible in a short time (no parental care, low survival rates, rapid population growth is possible with massive fluctuations in density, common of many insects/frogs/ fish)
k selected: a long time spent on producing and raising each offspring (lots of energy devoted to offspring care, high survival rates, slow population growth that is usually carrying capacity, most large mammals)
Why are isolated populations at greater risk of extinction than those that are close enough to one another for individuals to migrate between them?
Isolated populations do not have GENE FLOW with others.
The size is small and lack of genetic diversity. If a “bad “ gene is carried down, and is is not favorable, then offspring will not survive.
Why are unbalanced sex ratios especially problematic for the conservation of monogamous species of animals?
Individuals without mates can’t reproduce and pass down genes .
Survivorship curve might change birth / death. Decrease offspring and biodiversity.
What is exponential growth and why does it rarely last long?
Populations increase by a fixed amount every year
It rarely lasts long because populations overshoot their carrying capacity and limiting factors such as food , disease, space become an issue.
