Population Biology Notes

1. Population Biology Notes

2. Population Dynamics A group of same species living in an area Collection of several different species living in an area Size (# of individuals) Density (# of indiv. in a certain space) Dispersion (clumps due to resource availability) Age Distribution (# of indiv. at each age)

3. Population increase Population decrease immigration emigration capacity for growth rate of population growth if unlimited resources Reproduce at a very young age Reproduce many times Have many offspring at once Insects, sea stars, bacteria, rodents

4. The # of individuals of a certain species that can be sustained indefinitely in a given space -High reprod. rate -Generalized niche -Adequate food -Disease/parasite resistance -Highly adaptable -Low reprod. rate -Specialized niche -Inadequate food -Not disease/ parasite resistant -Low adaptablity

5. The population is constantly multiplying (ex  2, 4, 8, 16, 32, 64, 128….) J J Humans

6. A population that has reached carrying capacity S S Competition Immigration & Emigration Natural & man made catastrophes Seasonal fluctuations in resources

7. Affects population size regardless of population density -Natural Disasters -Unseasonable weather -Habitat destruction -Pesticide spraying Have a greater effect on population if more dense -Predation -Parasitism -Disease -Competition for resources

8. Size fluctuates only a little above or below carrying capacity (K) Usually stable population that temporarily goes way up and then crashes back to the stable number Possible causes: Better weather, more food, fewer predators Changes without any pattern (We don’t know the cause) Consistent changes of population size over a regular period of time

9. Predator Controls Example: -Lynx prey on snowshoe hares -Hare population goes down -Fewer hares = fewer lynx -Fewer lynx = hares increase Prey Controls Example: -Hares overeat their food supply -Hare population crashes -Less hares = more plants -More plants  more hares  more lynx **Big predators do Top-down control (wolves, big fish, sharks, alligators…)

10. -One parent -Offspring are identical genetic copies Examples: Bacteria, algae, fungi, plants, some animals -Two parents -Offspring are a combination of parents’ genes (½ mom, ½ dad) 97% of species reproduce this way!

11. -Females have to produce twice as many offspring to maintain same number (since males don’t give birth) -Chance of genetic errors/defects during splitting/recombination of chromosomes -Time consuming courtship & mating rituals -Disease transmission -Injury during mating -Greater genetic diversity in offspring (kid can be better genetically than either parent) -Males can gather food for female and offspring, can protect and train/teach young.

12. large small Very good Little/none Later Early survive die Large Small stable unstable Low High Fairly stable (around K) Fluctuates (above or below K) Large mammals, birds of prey, large & long-lived plants Bacteria, rodents, algae, insects, annual plants **PRONE TO EXTINCTION!!

13. 1970’s To preserve species and their ecosystems Which species is in danger of extinction? What is the status of the ecosystem and what value is there to humans and other species if lost? What measures can we take to help sustain ecosystems and viable populations of wild species?

14. population studies Measure current population size Project possible population size changes Determine if existing populations are sustainable

15. Breaking up and damaging habitats • Simplifying ecosystems by either only planting one species or letting weeds invade • Strengthening pest species and bacteria • Eliminating some predators • Introducing exotic species • Overharvesting renewable resources

16. Realize that everything is connected to everything else (web of life) • Reduce or minimize the damage we do to nature and heal the ecological wounds we have already caused • Use sustainable methods • Take no more than we need • Preserve biodiversity of plants and animals