Populations and Ecosystems

Ecosystem- includes all of the living things (plants, animals and organisms) in a given area, interacting with each other, and also with their non-living environments (weather, earth, sun, soil, climate, atmosphere).

Ecology- the branch of biology dealing with the relations and interactions between organisms and their environment

Biodiversity – the degree of variation of life. Variety of organisms present in different ecosystems.

Plants and animals need air, water, light (plants only), space, food and shelter…

these things can be found in their environment.

● Population - all the individuals of a given species in a specific area or region at a certain time.

● Community - refers to all the populations in a specific area or region at a certain time.

● Environment – the surroundings or conditions in which an organism operates.

● Habitat – the natural surroundings or environment in which an organism lives

Biotic and abiotic factors make up an ecosystem…

● Biotic Factor – are all the living organisms within an ecosystem

● Abiotic Factor – are all of the non-living things in an ecosystem (ex: pH, sunlight, turbidity, available nutrients, wind, etc.)

What is a niche?● Niche - the status of an organism within its environment

and community (affecting its survival as a species). It includes:

● The role a species has in its environment

● Its interactions with the biotic and abiotic factors of its environment

Coexistence and Competition ● Competition – occurs when a resource that is essential to

growth and reproduction occurs in short supply. It is an interaction that has a mutually negative effect on the participants.

● Coexistence – occurs when populations of several species that utilize the same limiting resources manage to persist within the same area.

Population Density ● It is a measure of the number of organisms that make up a

population in a defined area.

● What is its significance?

● Ecosystems function best when they have the correct number of organisms making up a population to utilize the resources available.

● Ideal number of a population = carrying capacity

● Population density = Population / Total land area

Limiting Factors● Environmental factors that limit population sizes in a

particular ecosystem.

● Examples:

● Food/nutrients

● Temperature

● Water

● Natural Resources

● Predation

Density Dependent Factors● Any factor limiting the size of a population whose effect is

dependent on the number of individuals in the population.

● Ex: Disease having a greater effect in limiting the growth of a large population, since overcrowding facilitates its spread.

Density Independent Factors● Any factor limiting the size of a population whose effect is

not dependent on the number of individuals in the population.

● Ex: Earthquake, impacts all members of a population regardless of whether the population is large or small.

8.L.3.2 Summarize the relationship among producers, consumers and decomposers, including the positive and negative consequences of such interactions including:Coexistence and cooperation CompetitionParasitismMutualism

● Three categorizes of the food chain:

● Producers

● Consumers

● Decomposers

They aredependent on

each other!!!

Producers● Producers get their food and energy from the sun.

● Plants

● They make their food through a process called photosynthesis

Consumers● Consumers need to eat their food to get energy

● Animals

● Three Types:

● Carnivores

● Herbivores

● Omnivores

What type are humans?

Consumer: Carnivores

● Only eat meat (other animals)

Consumer:Herbivores

● Herbivores only eat plants

Consumer:Omnivores

● Omnivores eat both meat (animals) and plants

Decomposer● Decomposers eat dead things and turn them back into dirt,

or soil.

● Ex: Mushrooms, worms, bugs

Symbiotic Relationship● Symbiosis – interaction between two species.

Sometimes beneficial, sometimes harmful…There are a few types:

● Commensalism

● Mutualism

● Parasitism

Commensalism● Commensalism - an association between two organisms

in which one benefits and the other derives neither benefit nor harm.

Mutualism● Mutualism - symbiosis that is beneficial to both organisms

involved.

Parasitism ● Parasitism - one species, the parasite, benefits at the

expense of the other, the host.

8.L.3.3 Explain how the flow of energy within food webs is interconnected with the cycling of matter (including water, nitrogen,

carbon dioxide and oxygen).

Flow of energy● What is the ultimate source of energy?

● The sun!

The flow of energy through ecosystems can be described and illustrated in food chains, food webs, and pyramids (energy, number, and biomass).

● Food Pyramid

Food Chain● Food chain – linear sequence of links in a food web

starting from "producer" species (such as grass or trees) and ending at apex predator "decomposer" species (like grizzly bears or killer whales).

● Simple

● Why are there fewer organisms at the top of the food chain?

Food Web● Food web - a system of interlocking and interdependent

food chains.

● More complex

● Interconnected

Energy Pyramid (Trophic Pyramid)

● Energy Pyramid – graphical model of energy flow in a community. ● Producers are at the bottom because they are able to transform

the sun’s energy into a large amount of plant energy through photosynthesis.

● Animals that eat plants are at the next level (primary consumers). They reply on plants for their energy.

● Animals that eat primary consumers are next (secondary consumers). They reply on primary consumers for most of their energy. The energy level of this section of the pyramid is smaller because most of the energy at the primary consumer level is used for their life processes and transformed to heat before these animals are consumed.

● Animals that eat secondary consumers make up the next level (tertiary consumers). They reply on secondary consumers for most of their energy. This energy level of the pyramid is even smaller than the others.

Energy Pyramid● How much energy is lost from one level to the next?

● 10 % of the original energy is left to feed the next level. 90 % of the available energy is used for life processes such as respiration, photosynthesis, and reproduction and transformed to heat energy before an organism is consumed.

● The amount of energy at each trophic level decreases as it moves through an ecosystem.

Cycling of Matter● The flow of energy is interconnected with the cycling of

matter.

● Matter, in the form of nutrients, also moves though the organisms at each level.  But matter cannot be replenished like the energy from sunlight.  The atoms of carbon, nitrogen, oxygen and other elements make up the bodies of organisms alive today are the same atoms that have been on Earth since life began.

● Matter is constantly recycled.

Cycling of Matter● Flow of energy within food webs is interconnected with the

cycling of matter including…

● Water

● Nitrogen

● Carbon Dioxide

● Oxygen

Cycling of Water

Cycling of Nitrogen

● Nitrogen cycle – how nitrogen moves between plants, animals, bacteria, the atmosphere, and soil in the ground.

● For nitrogen to be used by different life forms on Earth, it must change into different states. Nitrogen in the air, N2, nitrates (N03), nitrites (NO2), and ammonium (NH4).

● The most important part of the cycle is bacteria.

Bacteria helps nitrogen change between states so it can be used.

● Fixation - Fixation is the first step in the process of making nitrogen usable by plants. Here bacteria change nitrogen into ammonium.

● Nitrification - This is the process by which ammonium gets changed into nitrates by bacteria. Nitrates are what the plants can then absorb.

● Assimilation - This is how plants get nitrogen. They absorb nitrates from the soil into their roots. Then the nitrogen gets used in amino acids, nucleic acids, and chlorophyll.

● Ammonification - This is part of the decaying process. When a plant or animal dies, decomposers like fungi and bacteria turn the nitrogen back into ammonium so it can reenter the nitrogen cycle.

● Denitrification - Extra nitrogen in the soil gets put back out into the air. There are special bacteria that perform this task as well.

Cycling of Carbon Dioxide● Carbon Cycle – cycles describing the flow of essential

elements from the environment to living organisms and back to the environment again.

● All living things are made of carbon. Carbon is also a part of the ocean, air, and even rocks.

● Because the Earth is a dynamic place, carbon does not stay still. It is on the move!

Oxygen Cycle ● Almost all living things need oxygen. They use this oxygen

during the process of creating energy in living cells.

● Plants mark the beginning of the oxygen cycle. Plants are able to use the energy from the sun to convert carbon dioxide and water into carbohydrates and oxygen into a process called photosynthesis.

● Animals form the other half of the cycle, we breathe in O2 which we use to break carbohydrates down into energy in a process called respiration. CO2 produced during respiration is breathed out by animals into the air.

● http://northsaanich.sd63.bc.ca/pluginfile.php/6749/mod_resource/content/1/sp7_-_chapter_2.pdf