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 rate Birth 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

MUTUALISM A 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.

COMMENSALISM A 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 consumers Producers (make food) Producers (make food) Consumers (use food by eating producers or other consumers) 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 Simple Energy path through an ecosystem  Food Web More realistic path through an ecosystem made of many food chains More realistic path through an ecosystem made of many food chains

Food Chain

Food Web 25

Name the Producer, Consumers & Decomposers in this food chain: 26

Food Chain 27 Producer ( trapped sunlight & stored food) 1 st order Consumer 2 nd Order Consumer 3 rd Order consumer 4 th 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. Sunlight is the main source of energy for most life on earth. Producers contain chlorophyll & can use energy directly from the sun Producers contain chlorophyll & can use energy directly from the sun 29

Consumers Heterotrophs eat other organisms to obtain energy.  Omnivores (Humans) Eat Plants & Animals Eat Plants & Animals  Detritivores (Scavengers) Feed On Dead Plant & Animal Remains (buzzards) Feed On Dead Plant & Animal Remains (buzzards)  Decomposers Fungi & Bacteria Fungi & Bacteria 30

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Trophic Levels  Carnivores/Omnivores Make Up The Remaining Trophic Levels Make Up The Remaining Trophic Levels Each level depends on the one below it for energy. 32

Trophic Levels Each Level In A Food Chain or Food Web is a Trophic Level.  Producers Always The First Trophic Level Always The First Trophic Level How Energy Enters The System How Energy Enters The System  Herbivores Second Trophic Level Second Trophic Level 33

Consumers Heterotrophs eat other organisms to obtain energy. (e.g. animals)  Herbivores Eat Only Plants Eat Only Plants  Carnivores Eat Only Other Animals Eat Only Other Animals 34

Photoautotroph Producer That Captures Energy from the sun by: Photosynthesis Photosynthesis ○ Adds Oxygen to the atmosphere ○ Removes Carbon Dioxide from the Atmosphere 35 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 36

Ecological Pyramids Graphic Representations Of The Relative Amounts of Energy or Matter At Each Trophic Level May be: Energy Pyramid Biomass Pyramid Pyramid of Numbers 37

Energy Pyramid 38

Biomass Pyramid 39 Biomass – All organic material in an ecosystem.

40 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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