BIOL 111 Chapter Notes - Chapter 9: Genetic Drift, Chromosome, Sexual Reproduction
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POPULATION DYNAMICS AND CARRYING CAPACITY
1. Population dynamics is a study of how populations change in size, density, and age distribution.
2. Bio-magnification: if stable chemical persist as energy dissipates, they increase at high trophic levels.
3. Three general patterns of dispersion in a habitat are: clumped, uniform, or random distribution.
4. Why clumping?
The resources of a species needs vary greatly in availability from place to place.
Living in herds, flocks, or schools can provide better protection from predation.
Living in packs gives some predators (eg, wolves) a better chance of getting a meal.
Some animal species form temporary groups for mating and caring for their young.
5. Four variables govern changes in population size = (birth + immigration) – (death + emigration).
6. Populations vary in their capacity for growth, also known as the biotic potential of a population.
7. The intrinsic rate of increase (r) is the rate at which a population grows if resources are unlimited.
8. Individuals with high growth rates reproduce early, have short generation times, and many offspring.
9. Environmental resistance consists of all factors (eg, predators, space, nutrients) that limit growth.
10. Together, the biotic potential and environmental resistance determine the carrying capacity, K.
11. The carrying capacity (K) is the maximum # of individuals that can be sustained in a given space.
12. A population’s growth rate decreases as its size nears the carrying capacity as resources dwindle.
13. Reproductive time lag is time for birth rates to fall & death rates to rise when resources go scarce.
14. Population density is the number of individuals in a population found in a particular space.
15. The idea of maximum sustained yield is to harvest 50% of animals, while leaving enough to sustain.
16. In nature, there are four types of population fluctuations:
The stable population fluctuates in size slightly above and slightly below its carrying capacity.
Species with stable populations may occasionally irrupt to a high peak and then crash.
Cyclic fluctuations of population size rise and fall over a regular time period (eg, 3-4 years).
Irregular fluctuations of population size happen with no recurring pattern.
REPRODUCTIVE PATTERNS AND SURVIVAL
1. Asexual reproductive is when all offspring are exact genetic copies of a single parent (eg, bacteria).
2. Sexual reproduction is when organisms produce offspring by combining gametes from both parents.
3. Sexual reproduction has three disadvantages:
Males do not give birth. Females have to produce twice as many offspring.
There is an increased chance of genetic errors and defects during chromosome recombination.
Reproduction consumes time, transmits disease, and inflicts injury on males as they compete.
4. Sexual reproduction has two important advantages:
It provides a greater genetic diversity in offspring, increasing chances of reproduction.
Males of some species gather food for the female and young, as well as provide protection.