What is Ecology?

What is Ecology?

• * Ecology is the study of interactions among organisms and between organisms and their environment.

Levels of Organization• Biosphere – contains the combined portions of the

planet in which all of life exists, including land, water, and air/atmosphere. It is our planet as a whole and where ecology takes place.

• Biome – a group of ecosystems that have the same climate and similar dominant communities.

• Ecosystem – a collection of organisms that live in a particular place along with their non-living, or abiotic, environment.

• Communities – assemblages of different populations living together in a defined area.

• Populations – groups of individuals that belong to the same species and live in the same area.

• Organism – an individual living thing.

Example:

Whole Planet

↓

Temperate Forest↓

Pond, plants, animals, water, O2, rocks

↓

Pond, frogs, fish, plants, algae

↓

All bullfrogs in pond↓

Bullfrog

Biotic Factor = living organisms influencing the environment

Abiotic Factor = non-living influences on environment

Ecological Levels of Organization

A Hierarchy of Interactions

– Ecology can be divided into four increasingly comprehensive levels:

1. organismal ecology,

2. population ecology,

3. community ecology, and

4. ecosystem ecology.

(a) Organismal ecology

(b) Population ecology (c) Community ecology

(d) Ecosystem ecology

A Hierarchy of Interactions

• Organismal ecology is concerned with evolutionary adaptations that enable individual organisms to meet the challenges posed by their abiotic environments.

A Hierarchy of Interactions

– Population ecology• addresses populations, groups of individuals of the

same species living in a particular geographic area and

• concentrates mainly on factors that affect– population density and – growth.

A Hierarchy of Interactions

– Community ecology• is concerned with communities, all the organisms

that inhabit a particular area and• focuses on how interactions between species

affect a community’s– structure and– organization.

A Hierarchy of Interactions

– Ecosystem ecology• is concerned with ecosystems, all the abiotic

factors in addition to the community of species in a certain area and

• focuses on energy flow and the cycling of chemicals among the various abiotic and biotic factors.

Feeding Relationships

– Trophic structure is the feeding relationships among the various species in a community.

– A community’s trophic structure determines the passage of energy and nutrients from plants and other photosynthetic organisms

• to herbivores• and then to predators.

Feeding Relationships

• Autotrophs – Producers – produce their own food using sun or chemicals– Plants and algae - by photosynthesis (sun’s energy)– Some bacteria – by chemosynthesis (chemical energy)

• Heterotrophs – Consumers – rely on autotrophs for food– Herbivore – eat autotrophs directly (primary consumers)– Secondary consumers and up:

• Carnivore – eat herbivores• Omnivore – eat both autotrophs and heterotrophs• Scavengers – feed on carcasses• Detritivores – eat decaying plant and animal material• Decomposers – break down organic material and release nutrients

ProducersPlant

A terrestrial food chain An aquatic food chain

Phytoplankton

Herbivore

Carnivore

Carnivore

Carnivore Carnivore

Carnivore

Carnivore

ZooplanktonPrimaryconsumers

Secondaryconsumers

Tertiaryconsumers

Quaternaryconsumers

Food Chains• Food Chains – show the sequence of food transfer

between trophic levels

algae → zooplankton → small fish → squid → shark(notice direction of the arrowheads!!!)

• This food chain idea works for simple food chains but....

Food Webs

• …Food webs are able to show the complexity of more complicated ecosystems

• Food webs link all food chains in a community together

Quaternary,

tertiary,

and secondary consumers

Tertiary and

secondary consumers

Secondary and

primaryconsumers

Primaryconsumers

Producers(plants)

A Marsh Food Web

Biological Magnification

• Organisms can’t metabolize many of the toxins produced by industrial wastes or pesticides

• Toxins become concentrated as they pass through a food chain in a process called biological magnification.

Biological MagnificationFish-Eating Birds

Magnification ofDDT Concentration

10,000,000

100,000

10,000

1,000,000

1

1000

LargeFish

Small Fish

Zooplankton

Producers

Water

Energy Flow

• **** Sunlight is the main energy source for life on Earth.****

• *Energy flows through an ecosystem in one direction, from the sun or inorganic compounds to autotrophs (producers) and then to various heterotrophs (consumers). Energy is NOT reused.

• Chemical cycling is the use and reuse of chemical elements such as carbon and nitrogen within the ecosystem.

Energy flow

Lightenergy

Bacteria,protists,and fungi

Chemicalelements

Chemicalenergy

Heatenergy

Cm a c c ie i

hc l y l ng

Primary Production and the Energy Budgets of Ecosystems

– The amount, or mass, of living organic material in an ecosystem is the biomass.

– The rate at which an ecosystem’s producers convert solar energy to the chemical energy stored in biomass

• is primary production and• yields about 165 billion tons of biomass per year.

– Different ecosystems vary considerably in their primary production.

Open ocean

Algal beds and coral reefs

Estuary

Desert and semidesert scrub

Tundra

Temperate grassland

Cultivated land

Northern coniferous forest (taiga)

Tropical rain forest

Savanna

Temperate broadleaf forest

0

Average primary production(g/m2/yr)

500 1,000 1,500 2,000 2,500

Ecological Pyramids

• ****Pyramid of production (aka energy pyramid) – only roughly 10% of energy can be transferred to next trophic level because organisms use energy for respiration (breathing), movement, and reproducing. More levels between a producer and a top-level consumer means less energy remains from original amount = limited food chain length supported and more room needed for top level consumers****

Tertiaryconsumers

Secondaryconsumers

Primaryconsumers

Producers 10,000 kcal

1,000,000 kcal of sunlight

1,000 kcal

100 kcal

10 kcal

Ecological Pyramids

• Biomass Pyramid – shows amount of potential food for each trophic level (grams per unit area)

• Pyramid of Numbers – shows number of individuals at each trophic level.

Ecological Pyramids

Pyramid of NumbersShows the relativenumber of individualorganisms at eachtrophic level.

Biomass PyramidRepresents the amount ofliving organic matter at each trophic level. Typically, thegreatest biomass is at the base of the pyramid.

Energy PyramidShows the relative amount of energy available at each trophic level. Organisms use about 10 percent of this energy for life processes. The rest is lost as heat.