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• The branch of biology that studies the way living things interact with each other and with their physical environment.

• It looks at the ways an organism is affected by its surroundings and how the environment is affected by the presence and activities of the organisms.

• Ecosystems do not have clear boundaries. Things move from one ecosystem to another. They are composed of both biotic and abiotic factors.

Ecology

Living Things!

Factors that affect living things are:Biotic factors – things that are alive or were alive (Ex: the

plants, the animals, and the microorganisms)Abiotic factors – things that are non-living (Ex: water, air,

soil, temperature, light, and natural disasters)

The interaction of all biotic and abiotic factors creates an ecosystem.

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http://videos.howstuffworks.com/discovery/30707-assignment-discovery-abiotic-and-biotic-factors-video.htm

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Roles of Organisms

Organisms can be either producers, consumers or decomposers (detritivores) in terms of energy flow through an ecosystem.

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All living things need energy to survive and grow. The source of this energy is the sun.

Plants through photosynthesis (an endothermic process) create food (sugar), to store energy for later use.

To release stored energy from the sugar the plants carry out respiration ( an exothermic process).

Not all organisms can produce their own food, so some must depend on other organisms as a source of food (energy).

Two other important terms that are associated to ecosystems are: habitat and niche.

A niche is a way of life of an organism. It is its total role in the community. An organism’s niche can be thought of as its “profession” or “how it makes its living”.

Examples:Maple Tree:

absorb sunlight by photosynthesis; absorb water and mineral salts from the soil; provide shelter for many animals and plants; act as a support for creeping plants; serve as a source of food for animals; cover the ground with their dead leaves in the autumn.

Deer: feed on grass; become food for wolves; provide food

for black flies and mosquitoes; fertilize the soil with its wastes and so on…

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Habitat

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An organism’s niche determines its habitat.

Habitat refers to the actual place an organism lives. An organism’s habitat may be thought of as its “address”.  

Organism Habitat

Cactus Desert

Water Lily Pond

Organisms depend on one another for food.

Every organism belongs to one of the three main feeding levels:

producer, consumer, or decomposer.

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Producers:are self feeding organisms (autotrophs) that make organic molecules (glucose) during the process of photosynthesis. Photosynthesis uses energy from the sun plus the inorganic molecules CO2 and H2O. Examples: Algae, grasses, trees, etc.

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IN: CO2,sunlightwater

OUT: OxygenSugar

Photosynthesis

- Plants making food

IN: CO2,sunlightwater

OUT: OxygenSugar

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Consumers: are heterotrophs, organisms that

cannot make their own food, they depend on other living organisms for food.

Primary Consumers:

Herbivores that eat vegetation Ex. : Grasshoppers, rabbits, snails, etc.

Secondary Consumers:

Carnivores that eat the herbivores Ex. : cats, ladybugs, foxes, owls, etc.

Tertiary Consumers:

Top carnivores.Ex. : Lions, bears, wolves, etc. 14

The Decomposers (Detritivores) :

They decompose dead organic material or wastes to return essential nutrients to the soil. These nutrients help plants grow.Ex. : Bacteria and mushrooms

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Trophic (feeding) level Ecologists call feeding levels trophic levels.refers to the organisms position in the food chainAutotrophs are at the base (first trophic level).Organisms that eat autotrophs are called

herbivores or primary consumers (second trophic level).

An organism that eats herbivores is a carnivore and a secondary consumer. (third trophic level)

A carnivore that eats a carnivore that eats a herbivore is a tertiary consumer (forth trophic level).

Omnivores eat both animals and plants.

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Example of a food chain and the associated trophic (feeding) levels

Organisms Grasses Grasshopper Ladybug Raven Mushrooms

Bacteria

Type Producer

(plants)

Primary Consumer

(herbivore)

Secondary Consumer

(carnivores)

Teriary Consumer

(top carnivore)

Decomposer

Trophic Levels

First Second Third Fourth Feed off all levels

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Organism Classification

Consumer level

Trophic level

Food source

Plants ------------------ First ------------------

Herbivores primary Second plants

Carnivores secondary or higher (top)

Third animals

Omnivores all levels plants & animals

Detritivores --------------- ---------------- detritus 18

An overview of Trophic and Consumer levels

• Food Chains and Webs

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Food Chains

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Energy and Nutrient Flow Through the Ecosystem

The movement of energy is shown by the dark arrows.

The movement of the inorganic nutrients is shown by the open arrows

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Food Chains and Webs

A food chain is the path of food from a given final consumer back to a producer. (The arrow points to the consumer.)

grass grasshopper mouse snake hawk

Identify the autotrophs and heterotrophs, and classify each as a herbivore, carnivore, etc.

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Food Chains vs. Food WebsFood Chain - Sequence in which energy

is transferred from one organism to the next as each organism eats another.

Berries Deer Wolf

Food Web - shows all feeding relationships in an ecosystem

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Food Webs

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Identify the autotrophs and heterotrophs, and classify each as a herbivore, carnivore

The real world is more complicated than a simple food chain. A more realistic depiction of who eats whom is called a food web which depicts interlocking food chains.

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Questions to answerFrom the previous slide identify:1. Producers2. Primary consumers3. Secondary consumers4. Tertiary consumers5. Top carnivores

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ENERGYAt each level of the food chain, about 90% of

the energy consumed is lost in the form of heat. The total energy passed from one level to the next is only about one-tenth of the energy received from the previous level organism. As you move up the food chain, there is less energy available to pass on to the next level.

As you move up the food chain animals get larger and need more food to meet their energy needs.

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NOTE!! Each organism in the food chain is only transferring one-tenth of its energy consumption to the next organism.

To summarize

1. The ultimate source of energy (for most ecosystems) is the sun.

2. The ultimate fate of energy in ecosystems is for it to be lost as heat.

3. Energy and nutrients are passed from organism to organism through the food chain as one organism eats another.

4. Decomposers remove the last energy from the remains of organisms and release nutrients back into the soil.

5. Inorganic nutrients are cycled, energy is not.

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Ecological Pyramids: represent graphically the structure of an ecosystem

Pyramid of Energy Flow : shows the energy that flows through each trophic level; notice that there is less energy at each higher level.

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Pyramid of Numbers: shows the actual size of populations.

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Pyramid of Biomass: measures the biomass ( g/m² ) of the organisms in a food chain (dry mass).

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Feeding the human population is big business (effort and monetary)

To prevent crops from being eaten by insects, agriculture has turned to various chemicals that kill the insects or that interfere with their life-cycle (reproduction)

In small doses, these chemicals are not harmful to other organisms, however, when they enter the food chains and move to high trophic levels, the quantities accumulate and can cause harm.

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Bioamplification (Bio-magnification):

Accumulation of toxins in a food chain so that the major effects are found in the food predators.

Example: DDT: a pesticide used in the 50s and 60s to control populations of body lice, fleas and mosquitoes).Later used as a crop pesticide, after which sign of trouble appeared!!!!!

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DDT- Belugas- St. Lawrence River

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World’s Biomes

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All the Earth’s ecosystems make up what is called the ecosphere or biosphereClimate is the main factor that determines whether a given species will thrive in an area. Biologists have divided the terrestrial (land) portion of the biosphere into biomes (collection of ecosystems that are similar)

Biomes are large regions with a distinct climate and specific life forms Each biome is made up of many similar ecosystems with communities adapted to varieties in soil, climate and other factors throughout the biome.

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Biodiversity: the genetic diversity, species diversity and ecological diversity that are important to life on this planet. It is the results of adaptations in organisms that have developed over billions of years in response to: *the variety of environments found on earth

*competition amongst organisms for resources

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A PopulationGroup of organisms of

the same species living in the same place at the same time

Individuals may come and go, but the population can remain the same

Ex: The flamingos of Lake Victoria in Africa.Assembled for yearly

migration.

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In a food web, each organism survives by gaining energy from the trophic level below it. The size of the populations then, are continually adjusted by the species interactions with both its food supply and it’s predators.

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Carrying capacity: the largest population of a species that an environment can support.

4 main factors that determine the carrying capacity:1. materials and energy: energy, water, carbon, and other essential nutrients2. food chains: the population size is limited by the size of the populations at lower trophic levels. (Prey limited by their predators and their food supply).

3. competition: each organism has the same need as any other. They compete for resources such as food, water, mates, space.4. density: depending on their size, environment and way of life, different species have different needs for space.

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Closer look at competition:Two types of competition:

1. intraspecific: among members of the same species2. interspecific: between different species

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A closer look at population density:Two types of factors can also limit population sizes.

1. density-dependent factors: these are factors that increase as the population gets bigger and eventually lead to a decrease in the population size by increasing death rate and lowering birth rate.

* overcrowding*parasites/disease*aggression amongst members* neglect of offspring

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2. density-independent factors:can limit a population regardless of its original size.

* forest fire

* flood* volcano* weather: El Nino

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Population GrowthSince all organisms

reproduce, populations tend to grow over time

If unlimited resources are present, growth will be exponential

It will proceed very quickly for rapidly reproducing organisms and more slowly for slowly reproducing ones

The curve, however, will always be a “J” curve or an exponential growth curve

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Generation # of bacteria time1 1 02 2 15min3 4 30min4 8 45min5 16 1hr6 32 75min7 64 90min8 128 105min9 256 2hrs10 51211 102412 204813 4096 3hrs14 819215 16,38416 32,76817 65,536 4hrs18 131,07219 262,14420 524,28821 1,048,576 5hrs22 2,097,15223 4,194,30424 8,388,60825 16,777,216 6hrs

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Population Growth 2Resources are never

unlimited, though. As population rises, resources

decline.If the growth is too rapid,

resources are rapidly depleted and a population crash can occur

This pattern occurs often with many populations (including humans)

For example...

Gypsy moth caterpillar

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Population Growth 3More often what

happens is that the resources slowly decrease, the growth rate slowly increases, and they meet.

This point that they oscillate around is the carrying capacity of the environment for that particular organism

S - shaped curve

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What are the causes of the rapid growth of human populations?What are some possible consequences of this growth pattern?What will our future look like? (Remember the Reindeer?)

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