Ecology

Ecology

• Scientific study of the interactions between organisms and their environment

Levels of Study

• Organism– Individual– 1 turtle

Levels of Study

• Population• Individuals of the same species living in the same area

• All the turtles of the same species

Levels of Study

• Community• All the organisms living in an area

• All the turtles, plants, insects, algae, bacteria

Levels of Study

• Ecosystem• All the organisms and all the abiotic factors

• All the organisms & the soil, water, gases, minerals

Levels of Study

• Biosphere• All the organisms & all the abiotic factors on Earth

• Earth

Abiotic Factors

• Nonliving• Temperature• Climate• Soil type• Rainfall• Gases• Minerals

Biotic Factors

• Living• Predators• Parasites• Herbivores• Carnivores• Decomposers

Biomes

• Tropical rainforest• Tall trees• High temperature• Heavy rainfall

Biomes

• Savannas• Tropical• Grasslands• Scattered trees• High temperature

• Less rainfall than tropical rain forest

Biomes

• Temperate grasslands

• Grasses• Seasonal droughts• Occasional fires• Lower temperature & less rainfall than savannas

Biomes

• Deciduous forests• Deciduous trees• Oak, maple• Warm summers• Cold winters• Moderate rainfall

Biomes

• Taiga• Coniferous forests• Pines & firs• Cold winters• Heavy snowfall

Biomes

• Tundra• Grasses & sedges• Very cold winters• Permafrost• High winds• Little rain

Population Characteristics• Density• Number of individuals per unit area or volume

Population Characteristics• Dispersal Patterns

• Spacing between individuals

• Clumped• Uniform• Random

Population Characteristics• Dispersal Patterns

• Clumped

Population Characteristics• Dispersal Patterns

• Uniform

Population Characteristics• Dispersal Patterns

• Random (ferns)

Population Characteristics• Demographics• Study of vital statistics

• Age structure– Groupings by age– Graphed

• Sex ratio– % of females compared to males

Population Characteristics

Survivorship Curves

• Graph of # of survivors vs. relative age

Survivorship Curves

• Type I• Most survive to middle age

• Humans

Survivorship Curves

• Type II• Likelihood of death same at any age

• Squirrel

Survivorship Curves

• Type III• Most die young

• Oyster

Limiting Factors

• Prevent population from reaching biotic potential

• Types– Density dependent– Density independent

Limiting Factors

• Density dependent• Effect becomes more intense with increased density

• Examples– Parasites & diseases– Competition for resources– Toxic effect of waste products– Predation

Limiting Factors

• Density independent• Occur independently of density• Examples:

– Natural disasters– Climate extremes

Population Growth Models• Exponential Growth• Change in # of individuals (N) over time (t) is equal to the growth rate (r) times the number of individuals (N)

rNt

N=

Population Growth Models• Exponential Growth• J-shaped curve

Population Growth Models• Logistic Growth• When limiting factors restrict size of population to carrying capacity

• Carrying capacity (K) = max. # of individuals of a population that can be sustained by the habitat ⎟

⎠

⎞⎜⎝

⎛ −=

K

NKrN

t

N

Population Growth Models• Logistic Growth• Sigmoid (S) shaped curve

Life-History Strategies

• r-selected species• Exhibit rapid growth (J-curve)• Examples – grasses, insects• Characterized by opportunistic species

– Quickly invade habitat– Quickly reproduce– Then die

• Produce many offspring that are small, mature quickly, require little parental care

Life-History Strategies

• k-selected species• Population size remains relatively constant

• Example - humans• Produce small number of relatively large offspring that require extensive parental care

• Reproduction occurs repeatedly during lifetime

Community Interactions

• Interspecific Competition• Competition between different species• When 2 species compete for same resources one will be more successful

• To survive, the less successful species– Must use slightly different resources

– Must use resources during different time of day

Community Interactions

• Predation• Any animal that totally or partly consumes a plant or animal

• True predator kills and eats another animal

• Parasite lives in and off a host• Herbivore is an animal that eats plants

Community Interactions

• Symbiosis• Two species that live together in close contact

• Types– Mutualism– Commensalism– Parasitism

Community Interactions

• Mutualism• Both species benefit from relationship

• Examples– Bacteria in root nodules– Lichens – algae & fungus living together

Community Interactions

• Commensalism• One species benefits while the other is neither harmed nor helped

• Examples– Birds building nests in trees

– Egrets that eat insects around cattle

Community Interactions

• Parasitism• One species benefits while the other is harmed

• Examples– Tapeworm inside animal– Ticks on dog

Ecosystems – Trophic Levels• Primary producers

• Plants• Photosynthetic bacteria

• Algae

Ecosystems – Trophic Levels• Primary consumers

• Herbivores• Eat producers

Ecosystems – Trophic Levels• Secondary consumers

• Carnivores• Eat primary consumers (herbivores)

Ecosystems – Trophic Levels• Tertiary consumers

• Secondary carnivores

• Eat secondary consumers

Ecosystems – Pyramids

• Pyramid of numbers

• Most = producers

• Least = top level consumers

Ecosystems – Pyramids

• Pyramid of energy• Most = producers• Least = top level consumers

Ecosystems – Pyramids

• 10% rule• Only 10% of energy available at each trophic level is converted into new biomass at the next level

Ecosystems – Food Chain

Ecosystems – Food Web

Nitrogen Cycle

Water Cycle

Carbon Cycle

Human Impact

• Greenhouse effect• Ozone depletion• Acid rain• Deforestation• Pollution• Species extinction