Ecosystem Interactions Honors Biology Chapter 14

Where & how organisms live Range- geographical reach Habitat- where Ecological Niche- how

Niche includes food, abiotic conditions, behavior Competition results when species, in the same community, overlap in use of resources – Strong selective force – Competitive exclusion Banishment/extinc tion Evolution Niche partitioning

Niche (resource) partitioning

Ecological Equivalents – same niche…different communities Convergent evolution’s fingerprint

Predation – Another interaction with highly selective outcomes

Symbiosis – a kinder interaction, tho’ not without an evolutionary punch Mutualism – both benefit Parasitism – parasite benefits, host harmed Commensalism – one benefits, the other unaffected

Population Dynamics Population: all the individuals of a species that live together in an area Demography: the statistical study of populations, make predictions about how a population will change

Population Dynamics Three Key Features of Populations Size Density Dispersion (spatial distribution)

Three Key Features of Populations 1. Size: number of individuals in an area

Influences on Population Size SurvivorshipReproductive Strategies 1. R Strategists  short life span, small body, reproduce quickly, many young, little parental care 2. K Strategists  long life span, large body, reproduce slowly, few young, parental care,

Three Key Features of Populations 2. Density: measurement of population per unit area or unit volume Formula: D p = N/S Pop. Density = # of individuals ÷ unit of space

Human Population Density

Three Key Features of Populations 3. Dispersion: describes their spacing relative to each other clumped uniform random

Clumped for protection, resources, mating or social interaction Uniform dispersion due to intraspecies competition / territoriality 3. Dispersion: describes their spacing relative to each other Three Key Features of Populations Random dispersion implies absence of interaction - rare. Mature communities.

Patterns of Dispersion

Population Growth Patterns Growth Rate: Birth Rate (natality) - Death Rate (mortality) How many individuals are born vs. how many die Birth rate (b) + Immigration rate (i) − death rate (d) = rate of natural increase (r). Total Growth must add immigration & subtract emigration statistics

Population Growth Patterns Exponential – J shaped curveLogistic – S curve

Population Growth Patterns The “Boom Bust” Curve

World Human Population Growth

Other Factors Affecting Population Growth Age Structure POST-REPRODUCTIVE REPRODUCTIVE PRE-REPRODUCTIVE

Age Demographics for Three Countries

Immigration and Emigration Can Strongly Effect Population Dynamics Estimated rates of US population growth with or without immigration. Immigration & Emigration Influences on Total Rate of Growth

Demographic Transition The move from “Developing” to “Developed” Country

Other Factors Affecting Population Growth Carrying Capacity- the maximum population size that can be supported by the available resources –There can only be as many organisms as the environmental resources can support

Carrying Capacity Carrying Capacity (k) Time J-shaped curve (exponential growth) S-shaped curve (logistic growth) #

Other Factors Affecting Population Growth Limiting Factors - any biotic or abiotic factor that restricts the existence of organisms in a specific environment.

Two Types of limiting Factors 1. Density-dependent factors- increase effect as population size increases. (disease, competition, parasites) 4. Density-independent factors- affecting populations regardless of their density (temperature, storms, habitat destruction, drought)

Gradual, sequential change in an area that regenerates or creates a community an area Succession at Mt. St. Helens. Ecological Succession Succession after the Yellowstone fires.

Primary succession: occurs where life has not previously existed Retreating Glaciers at Glacier Bay Alaska

Primary Succesion – Very Slow

Secondary Succession – Faster (soil already present) Mount St. Helens

Succession Climax Community theoretical end-point of succession. Stable community.