Ecology is study of interactions between • non-living components in the environment…

– light – water– wind– nutrients in soil– heat– solar radiation– atmosphere, etc.

AND…

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• Living organisms…– Plants– Animals– microorganisms in soil, etc.

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The ENVIRONMENT is the sum of all the surroundings that an organism lives in.

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The levels of ecological organization are:

Organism

Population

Community

Ecosystem

Biome

ORGANISMS are complete and living things. They are the smallest unit of ecological study.

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A POPULATION is a group of individual organisms of the same species living in a particular area at a particular time.

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All the organisms that inhabit a particular area are called COMMUNITIES.

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An ECOSYSTEM includes all the BIOTIC and ABIOTIC factors in an area.#6

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A BIOME is a large geographical area controlled by climate and distinguished by different plants and animals.

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Ecologists Study Relation ships13.1

Population density

Population density is the number of individuals of a particular species per unit area or volume.

Calculating population density

Population density =

number of individuals / unit area

An example: One could count all the polar bears living in the Arctic National Wildlife Refuge. Let’s assume this was done, and it was determined that 1125 polar bears live in ANWR. The land area of ANWR is 46,943 square kilometers.

Population density (polar bears in ANWR) = number of individuals / unit area =

1125 polar bears / 46,943 sq km =

0.023 polar bears / sq km, or

1 polar bear / 41.7 sq km (km2)

Population density could be the number of alligators per square kilometer of swamp, the number of bacterial colonies per square centimeter on an agar plate, or the number of people per square mile.

Sampling techniques

• Quadrats• Indirect counting• Mark-recapture

Quadrats

• Quadrats are square or rectangular areas measured off in order to determine the number of individuals of a given species, or the number of species, etc., in the specified area.

Indirect counting

• Indirect counting is a sampling technique used for counting organisms that for whatever reason(s) are difficult to count directly. Items indicating the presence of the organism, such as tracks, burrows, nests, etc. are counted instead of the animals themselves. For instance, instead of counting polar bears, an ecologist might count the number of polar bear dens.

Mark-recapture

• Mark-recapture is another commonly used technique to estimate population size or density. In this method, scientists capture and mark individuals of the study species, then release them. After some period of time, the scientists again capture animals from the study population and count the number of marked individuals.

Mark-recapture

Mark-recapture population calculation

• Total population =

[number in first capture (marked) x number in second capture] / number of marked individuals in second capture

13.2

Biotic and Abiotic Factors

The living parts of the environment are called the BIOTIC FACTORS.

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ABIOTIC factors are the nonliving aspects of the environment. ( also known as the physical environment) Abiotic components of the environment include rainfall, soil, wind, water temperature, fire, altitude, severe disturbance etc. Organisms tend to seek environments most suitable for themselves.

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Biodiversity is the variety or assortments of living things in an ecosystem #11

A Keystone species is a species that has an unusually large effect on an ecosystem.

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13.3

Energy in Ecosystems

What is a producer?

• Autotrophs/ producers are organisms capable of converting energy from sunlight into chemical energy in the form of food that can be used by other organisms.

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What is a consumer?

A consumer/HETEROTROPHS is

an organism that eats producers or other consumer organisms.

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Chemosynthesis is the process by which some organisms use chemicals, rather than light, to produce an energy source.

These organisms are found at the bottom of the oceans near volcanic vents

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13.4Food Chains and Food Webs

Food chain

• The pathway of food transfer from one trophic level to another.

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Food web

• A food web is a pattern of feeding represented by interconnected and branching food chains.

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#18 Herbivores are organisms that eat plants

• Carnivores are organisms that eat meat

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Omnivores are organisms that eat both plants and animals.

Detritus

• Detritus is the accumulated waste from organisms and remains of dead organisms.

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Decomposers• Decomposers are

consumers that obtain energy by feeding on and breaking down detritus.

• They function as vital recyclers of chemicals in ecosystems.

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A SPECIALIST is a consumer that primarily eats one specific organism or feeds on a very small number of organisms.

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A generalist is a consumer that eats a variety of different types of organisms.

Trophic level

A trophic level a step in the food chain or food web.

Three levels are:Primary, secondary and

tertiary

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13.5

Cycling of Matter

Basic Pattern of Chemical RecyclingChemical cycles typically involve three general steps:

1. Producers incorporate chemicals from the nonliving environment into organic compounds.

2. Consumers feed on the producers, incorporating some of the chemicals into their own bodies and releasing some back to the environment in waste products.

3. As organisms die, decomposers break them down, further supplying the soil, water, and air with chemicals in inorganic form. The producers gain a renewed supply of raw materials for building organic matter, and the cycles continue.

In addition, at least part of each chemical's cycle involves nonliving processes such as rain and fires.

Water cycle

• Water vapor in atmosphere– Clouds

• Rain

• Precipitation• Organism uptake• Groundwater• Evaporation• Transpiration

The HYDROLOGIC or WATER CYCLE involves the movement of water from the atmosphere to the earth and back to the atmosphere. The sun's energy evaporates water from land and water surfaces, adding gaseous water vapor to the atmosphere. As it cools, water vapor condenses and eventually falls as precipitation (rain, snow, hail, or sleet). Plants absorb this fresh water from the soil, and consumers obtain water by eating and drinking.

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Water cycle

A BIOGEOCHEMICAL CYCLE is the movement of a particular chemical through the biological and geological, or living and nonliving, parts of an ecosystem.

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The Carbon-Oxygen CycleProducers use the carbon and oxygen atoms of these inorganic compounds to form organic compounds during photosynthesis Some of this organic carbon cycles to consumers as food.

During cellular respiration, both producers and consumers break down organic compounds such as sugars and release carbon dioxide gas as a waste product. Carbon dioxide also is released to the atmosphere as decomposers break down detritus.

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The NITROGEN CYCLE is the cycling of nitrogen between the atmosphere and the soil. #28

Certain types of bacteria convert the nitrogen gas to ammonia (NH3) through a process called nitrogen fixation

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Nitrogen fixation

• Nearly 80% of the atmosphere is nitrogen (N2), but…

• Most plants can only use nitrogen in the form of compounds such as ammonia (NH3) and nitrate (NO3).

• Bacteria in the soil can convert ammonium to nitrates in a process called nitrification, making nitrogen available to plants for growth.

The Phosphorus Cycle is the cycling of phosphorus from rocks to consumers

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13.6

Pyramid Models

Biomass

• The organic material made by producers is biomass.

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Biomass pyramid

• Represents the actual biomass at each trophic level of an ecosystem.

• In some systems, organisms may consume producers so rapidly, and survive long enough, that there is more biomass of the consumers than of the producers.

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Biomass vs. food pyramids• Differences

– One follows mass, the other energy

– A food (energy) pyramid always shows loss from one trophic level to the next.

– A biomass pyramid may, under special circumstances, show increase from one level to the next.

• Similarities– Both follow trophic

levels– Tend to have less

(mass or energy) at each higher trophic level

– Depend on the action of producers as the base of the structure

Energy pyramid

• Sometimes called a food pyramid, an energy pyramid is a diagram showing the energy loss from one trophic level to the next.

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Pyramid of numbers

• A diagram that depicts the numbers of individual organisms in each trophic level of an ecosystem.– Emphasizes how few

top-level consumers an ecosystem can support.

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