INTERACTIONS IN ECOSYSTEM

Populations in Ecosystems

A population is a group of organisms that belong to the same species and lives in a particular place at the same time.

Abundance – the number of individuals.

Density – how crowded. Number of organisms per unit area.

What influences a population?

Life expectancy

Death rateBirth rate

GROWTH RATE OF POPULATION

= BIRTH RATE – DEATH RATE

Populations constantly fluctuate, particularly populations that are linked in a predator prey relationship.

Predator – uses another organism as a food source.

Prey - an organism that is eaten as a food source.

Predator Prey

PREDATOR PREY

Interrelationships among Organisms Some organisms compete for the

same resources, and live together in a community, so have words to describe the relationships between organisms:

SYMBIOSIS Where two different species live together in

a close association. The association benefits at least one of

them and the other is not disadvantaged.

There are two common types of symbiosis

MUTUALISMA relationship between two organisms in which both benefit.

The alga and fungus make up lichen .

The alga provides food and oxygen for photosynthesis.

The fungus provides the moist environment necessary for the alga.

All grazing herbivores rely on symbiotic bacteria or protozoa in their digestive system.

Bacteria in the digestive system can digest cellulose.

The bacteria have a habitat with a constant environment and amply supply of food.

The kangaroo obtains access to an additional food source.

COMMENSALISMA relationship between two organisms in which only one

benefits and the other is unaffected.

The anemone fish and the sea anemone

The anemone fish live among the tentacles and gain protection from predators.

The anemone appears to receive no benefit.

Aphids are small, soft-bodied, near defenseless insects that feed on plant sap. They feed by inserting a pointed, strawlike mouth structure called a stylus into the vascular tissues (internal piping) of the plant and sucking the plant juices out. Plant sap, a combination of water and sugars, is low in other nutrients, however, and the aphid must process a great deal of plant sap in order to get the amino acids and other nutrients it needs. Most of the sugars and water, therefore, are excreted as waste through a pair of structures called cornicles located near the rearend of the insect.

The remora fish & the shark The remora gains a

free ride and feeds on scraps from the shark’s food but appears to be of no service to the sharks.

PARASITISM A relationship in which one organism

lives in or on another and feeds from it. The organism in which a parasite lives in

or on is called the host. Well adapted parasites cause little harm

to their host. Their host remains healthy and able to provide them with a habitat and food.

Tapeworm Many tapeworms

live attached to the lining of the digestive system of their host animal and absorb digested food without casing any serious harm.

HYDATIDS Other parasites

irritate their host and some cause disease which can kill their host. Disease causing parasites are called pathogens.

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Food webs Energy in an ecosystem

originally comes from the sun Energy flows through

Ecosystems from producers to consumersProducers (make food)Consumers (use food by eating producers or other consumers)

Feeding Relationships

Energy flows through an ecosystem in one direction

from producers to various levels of consumers

Feeding Relationships Food Chain

Simple Energy path through an ecosystem

Food WebMore realistic path through an ecosystem made of many food chains

Food Chain

Food Web

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Name the Producer, Consumers & Decomposers in this food chain:

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Food Chain

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Producer (trapped sunlight & stored food)

1st order Consumer

2nd Order Consumer

3rd Order consumer

4th Order Consumer

Niche of a Producer Captures energy and

transforms it into organic, stored energy for the use of living organisms.

May be photoautotrophs using light energy (e.g. plants)

May be chemoautotrophs using chemical energy (e.g. cyanobacteria) 28

Producers• Sunlight is the main source of energy for most life on earth.

• Producers contain chlorophyll & can use energy directly from the sun 29

ConsumersHeterotrophs eat other

organisms to obtain energy. Omnivores (Humans)

Eat Plants & Animals Detritivores (Scavengers)

Feed On Dead Plant & Animal Remains (buzzards)

DecomposersFungi & Bacteria

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Trophic Levels Carnivores/Omnivores

Make Up The Remaining Trophic Levels

Each level depends on the one below it for

energy.32

Trophic LevelsEach Level In A Food Chain or

Food Web is a Trophic Level. Producers

Always The First Trophic Level

How Energy Enters The System

HerbivoresSecond Trophic Level

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ConsumersHeterotrophs eat other

organisms to obtain energy. (e.g. animals)

HerbivoresEat Only Plants

CarnivoresEat Only Other Animals

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PhotoautotrophProducer That Captures

Energy from the sun by:Photosynthesis

○Adds Oxygen to the atmosphere

○Removes Carbon Dioxide from the Atmosphere

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Algae

Autotrophs An Autotroph is any

organism that can produce its own food supply!

Autotrophs are also called Producers

Plants, algae, some protists, & some bacteria are examples

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Ecological PyramidsGraphic Representations Of

The Relative Amounts of Energy or Matter At Each

Trophic LevelMay be:

Energy PyramidBiomass Pyramid

Pyramid of Numbers37

Energy Pyramid

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Biomass Pyramid

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Biomass – All organic material in an ecosystem.

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Natural Cycling of Ecosystems

Ecosystems are important because of the way that they are cyclic in terms of resources and nutrients

We can track the flow of these things through the ecosystem by studying different cycles:

-- Water cycle

-- Carbon Cycle

-- Nitrogen Cycle

-- Oxygen Cycle

-- Energy cycle

-- this includes food webs, chains, and pyramids

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