Concept check

• The constant, spring-fed stream. In more constant physical conditions, where populations are more stable and competition for resources is more likely, larger well provisioned young, which are more typical of iteroparous species, have a better chance of surviving.

• The territorial species likely has a uniform pattern of dispersion, since the interactions between individuals will maintain constant space between them. The flocking species is probably clumped, since most individuals probably live in one of the clumps (flocks).

• Type III

• The mark and recapture method involves marking a number of individuals in a natural population, returning them to that population, and subsequently recapturing some of them as a basis for estimating the size of the population at the time of marking and release. This procedure was first used by
C.J.G. Petersen.

• By preferentially investing in the eggs it lays in the nest, the peacock wrasse increases their probability of survival. The eggs it disperses widely and does not provide care for are less likely to survive, at least some of the time, but require a lower investment by the adults. (In this sense, the adults avoid the risk of placing all their eggs in one basket.)

• Simplest model for population growth is one with unrestrained growth.
• No predation, parasitism, or competition.
• No immigration or emigration
• Environment with unlimited resources.
• This is characteristic of a population that has been recently introduced into an area, such as bacteria newly inoculated onto a petri dish.
• Usually short-lived
• Even though the human population has been in this for over 300 years.

• Food and space

• Density-dependent factors are those factors that increase directly as the population density increases. They include competition for food, the buildup of wastes, predation, and disease.
• Density-independent factors are those factors whose occurrence is unrelated to the population density. These include earthquakes, storms, and naturally occurring fires and floods.

R-strategists
• Many young
• Little or no parenting
• Rapid maturation
• Small young
• Reproduce once
• Example: insect
K-strategies
• Few young
• Intensive parenting
• Slow maturation
• Large young
• Reproduce many times
• Example: mammals

• Competition—G.F Gause developed the competitive exclusion principle after studying paramecium.
• His principle states that two species cannot coexist in a community if they share a niche, that is, if they use the same resources.
• In nature, there are two related outcomes, besides extinction, if two species inhabit the same niche and therefore compete for resources. One species will evolve through natural selection to exploit different resources.
This is called resource partitioning. Another possible outcome is what occurred on the Galapagos islands.
Finches evolved different beak sizes to eat different of food and avoid competition. This is called character displacement

• Predation
– Plants evolved spines and thorns and chemicals
– Animals evolved active defenses such as hiding, fleeing, or defending.
– Animals also evolved passive defenses—coloration or camouflage.
• Aposematic—very bright, often red or orange (poison)
• Batesian mimicry—copycat coloration…mimic poisonous animals
• Mullerian mimicry—two or more poisonous species resemble each other and gain an advantage from their combined numbers.