Populations

Question 1

What is a population?

Answer 1

Group of organisms of the same species, living in the same place, at the same time

Question 2

What are the 2 population sampling methods?

Answer 2

Samples must be random: every individual has the same probability of being counted (improves reliability if sample represents the whole population)

Peterson sampling technique: capture, mark, release, recapture, calculate
The percent marked in recapture is the percent initially marked (10/100 marked = 1000 total)
Efficacy: doesn’t work if animals can avoid recapture, if birth/death occurs, if incorrectly marked

Quadrat technique: square device placed randomly with number generator in predetermined parameter, count number of organisms per quadrat, average and apply to whole area
Efficacy: assumes whole area is equal density, doesn’t work for mobile things

Question 3

What is a species? crossbreeding? how can species develop? (characteristic types)

Answer 3

Species: similar physiological (autotroph, warm blooded) and morphological (bipedal, fur) characteristics, can fertily interbreed, genetically distinct from other species, common phylogeny

Crossbreeding: breeding infertile animals between species (mule, liger)

Populations of the same species can develop into different species if they isolated and develop different characteristics

Question 4

Nutrition vocabulary: autotroph? heterotroph? mixotroph? consumer? detritivores? saprotroph?

Answer 4

Autotroph: self feeding

Heterotroph: feed on other organisms

Mixotroph: not exclusively auto- or hetero- (some unicellular)

Consumers: heterotrophs which feed on living organisms via digestion

Detritivores: heterotrophs which use digestion on dead material (dead leaves, fur, feathers)

Saprotroph: heterotrophs which use external digestion (excrete enzymes, decomposers)

Question 5

What are some challenges with defining populations through reproduction?

Answer 5

Salamanders in California live in horseshoe shape, can mate with direct neighbors but not ones living across path

2 populations could theoretically interbreed but don’t live together (unethical to test)

Difficult to use metric for asexually reproducing organisms

Some individuals are infertile or use in vitro fertilization

Question 6

What is the population growth curve and phases?

Answer 6

Births and immigration increase population, deaths and emigration decrease population

Population growth curve is a sigmoid (S shape)
1) exponential phase: increase natality and decrease death, lots of food / resources, little disease / predators
2) transition phase: decrease natality and / or increase death, natality > death
3) plateau phase: natality = death
k = carrying capacity, maximum population sustained by ecosystem

Paramecia have a “normal” curve when cultured
Daphnia have an overshot curve when cultured

Question 7

What 7 factors limit population size?

Answer 7

Food / nutrients / light

Territory (fight other organisms)

Nesting sites

Predation

Toxic waste (from humans, build up from lack of decomposition)

Stress (especially in intelligent organisms)

Weather / climate events, Climate Change