What is Ecology? Scientific study of the interactions of organisms with their abiotic and biotic environments... ...in order to understand the distribution and abundance of organisms in space and time.

Fields of Ecology Organismal Ecology (physiology, behavior) Population Ecology (life history strategies, demography, population growth) Community Ecology (species interactions, biodiversity) Ecosystem Ecology (energy & nutrient flow, landscape ecology)

Population Ecology A population is a group of individuals of the same species that live in a particular area and have the potential to interbreed. Flock of Starlings at Dusk – U.K.

Life History Characteristics Growth Change of form Dispersal Timing of reproduction Size at birth or germination Number and size of offspring Age at death

Life History - Growth Growth – for at least part of their life history, all organisms grow by assimilating energy and nutrients – final body size species-specific.

Life History – Change of Form Change of form - many organisms have dramatically different forms or stages in their life cycle.

Life History - Dispersal At some time in their lives, most organisms go through dispersal – enhances reproductive success. Belding’s Ground Squirrel Spiders Milkweed

Life History Characteristics Growth Change of form Dispersal Timing of reproduction Size at birth or germination Number and size of offspring Age at death

LIFE HISTORY STRATEGIES (LHSs): Patterns of lifespan and reproduction that characterize a species. LHSs are a result of natural selection, which acts on individuals, NOT species

Individuals that have a life history that maximizes fitness will be favored by natural selection… …thus, particular patterns of survival and reproduction will eventually be shared by all members of a population.

Three Main Life History Strategies: Survivorship Maturity Reproductive Output

3) Reproductive Output Parity # reproductive episodes in lifetime

Semelparous species Salmon Mayfly Agave Mayflies in order Ephemeroptera (“ephemeral”) – live only 24 hrs, do not even feed Agave Semelparous species

Iteroparous Species

3) Reproductive Output Parity Fecundity # offspring per reproductive episode

elephants rodents spiders

3) Reproductive Output Parity Fecundity Parental Investment Energetic effort put into offspring: Size of offspring

Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce. Other types of plants produce fewer large seeds that provide a large store of energy that will help seedlings become established.

Number of Offspring Offspring Size General Relationship between Offspring Size and Number of Offspring Many Number of Offspring Few Small Large Offspring Size

3) Reproductive Output Parity Fecundity Parental Investment Energetic effort put into offspring: Size of offspring Parental care

LHS of a hypothetical “super-organism”?

Real LHSs are compromises in the allocation of energy! Reproductive Trade-offs: Reproduction vs Future Survival

Reproduction vs Survival (Mortality)

How does caring for offspring affect parental survival in kestrels? 100 Male Female 80 60 Parents surviving the following winter (%) 40 20 Reduced brood size Normal brood size Enlarged brood size Fig. 53-8

Reproductive Trade-offs: Reproduction vs Future Survival Reproduction vs Future Growth Current vs Future Reproduction

Annual Meadowgrass Current vs Future Reproduction vs Future Growth

Particular combinations of LHSs often favored in particular body sizes… …but there are always exceptions to the rule!

Big Brown Bat (Eptesicus fuscus) Baby bat Longer lifespan (14 yrs) and lower fecundity (1-2) than expected for a mammal of that size (small)

A few, large offspring. Parental care in carrion beetles; very unusual for an insect.

“Octomom”

LHSs characterize species, but can also be somewhat flexible – different populations can adapt to different environmental conditions…

e.g. Fat-tailed Dwarf Lemur Pop 1: dry forest, long torpor (6-7 months): Fewer, smaller litters. Pop 2: rainforest, shorter torpor (4-5 months) and higher mortality rates: More frequent, larger litters.

Trade off between longevity and number of offspring: Long life span selects for low reproductive investment. Short life span selects for high reproductive investment

DEMOGRAPHY The study of birth and death processes that determine growth and age structure of a population.

Each age class of a population has an expected: Mortality rate Fecundity rate

Demographic characteristics can be represented in: Life Tables summarize deaths and/or births in different age classes of a population Conventional life table

Demographic characteristics can be represented in: Life Tables summarize deaths and/or births in different age classes of a population Conventional life table Diagrammatic life table (flow diagram)

2) Survivorship Curves Fig. 53-6 Number of survivors (log scale) 1,000 100 II Number of survivors (log scale) 10 Figure 53.6 Idealized survivorship curves: Types I, II, and III III 1 50 100 Percentage of maximum life span Fig. 53-6