Ch 8: Population Ecology

Population Dynamics and Carrying Capacity  Most populations live in clumps due to resource availability, protection, food capture, mating and/or caring for young.  4 variables in population changes: Birth, death, immigration, emigration

Population Dynamics and Carrying Capacity  Limits to population growth Biotic potential: Intrinsic rate of increase:  Species with high intrinsic rate of increase reproduce early in life, have short generations, reproduce many times and have many offspring.  Ex: Housefly (5.6 trillion in 13 months)

Population Dynamics and Carrying Capacity  No population can grow indefinitely due to limiting factors. Environmental resistance: Carrying capacity (K): Exponential growth: Logistic growth:  Occurs when populations encounter environmental resistance.

Reproductive Patterns  Asexual reproduction:  Sexual reproduction: Disadvantages  Males don’t give birth (females have to produce twice as many offspring)  Increased chance of genetic errors  Courtship and mating consume energy, can transmit disease, and can inflict injury to competing males. Advantages  Provides a greater genetic diversity (adapt better to changing environments)  Males of some species can gather food for female and young and help train young.

Reproductive Patterns  Opportunists and Competitors R-selected species (opportunists):  Ex: algae, rodents, insects K-selected species (competitors):  Ex: large animal; elephants, whales, humans  Prone to extinction Most species are between the 2 extremes.

Reproductive Patterns  Survivorship curves: Short to Long Lives Survivorship curve: 3 types  Late loss  Early loss  Constant loss