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Biology I Comp 3 Review. Organisms and Their Environments. Introduction to Ecology . Ecology is the study of organisms and their interactions with their environment. The environment includes 2 types of factors: Biotic factors – the living parts of the environment

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Biology i comp 3 review

Biology IComp 3 Review

Organisms and Their Environments

Introduction to ecology
Introduction to Ecology

  • Ecologyis the study of organisms and their interactions with their environment.

  • The environment includes 2 types of factors:

    • Biotic factors – the living parts of the environment

      • Plants, animals, bacteria, fungi, etc

    • Abiotic factors – the nonliving parts of the environment

      • Water, oxygen, light, temperature, etc.

Nutrient cycles
Nutrient Cycles

  • Some abiotic factors are nutrients that are needed by plants and animals to survive.

  • These nutrients are cycled through the ecosystem.

    • Helps maintain homeostasis, or balance, within the environment.

  • The 3 main nutrient cycles are:

    • Water

    • Carbon

    • Nitrogen

Water cycle
Water Cycle

  • Evaporation – water changing from a liquid to a gas

  • Transpiration – water evaporating from the leaves of plants

  • Condensation – water changing from a gas to a liquid

  • Precipitation – water returning to the land in the form of rain, sleet, hail, or snow

Carbon cycle
Carbon Cycle

  • Photosynthesis and Cellular Respiration cycle carbon and oxygen through the environment

    • Photosynthesis uses CO2 and produces O2

    • Respiration uses O2 and produces CO2

  • Carbon may be returned to the soil through decomposition

  • Carbon may also returned to the atmosphere through volcanic activity and burning fossil fuels

Nitrogen cycle
Nitrogen Cycle

  • Most Nitrogen is found in the atmosphere, but organisms can’t use it in that form

  • Atmospheric Nitrogen is made usable for living things through Nitrogen Fixation

    • Nitrogen-fixing bacteria on the roots of some plants

    • Lightning strikes

  • Denitrification – other bacteria in the soil can convert “fixed” nitrogen back into Nitrogen gas (N2)

Nitrogen cycle1
Nitrogen Cycle

  • Assimilation – Plants use Nitrogen in the soil to form amino acids and other organic compounds

    • Consumers obtain Nitrogen from eating producers

  • When plants and consumers die, decomposers return the Nitrogen to the soil

Levels of Organization

- Ecologists can look at the world in levels of increasing complexity







Levels of organization
Levels of Organization

  • Organism –

    • Any unicellular or multicellular form that exhibits all the characteristics of life

    • An individual

    • Example: A zebra

  • Population–

    • A group of organisms of the same species that live together in a certain area

    • Interbreed and compete for resources

    • Example: A herd of zebras

Levels of organization1
Levels of Organization

  • Community –

    • Groups of organisms of differentspecies that live together in a certain area

    • Example: A herd of zebras, a pride of lions, & a pack of hyenas

  • Ecosystem–

    • All the living and nonliving things in a certain area

    • Communities and the abiotic factors with which they interact

    • Example: Zebras, lions, hyenas, rocks, air, water, etc.

Levels of organization2
Levels of Organization

  • Biome

    • a group of ecosystems that have similar climates and communities

    • Example: Savanna

  • Biosphere

    • the entire portion of the planet that supports life


  • Aquatic

  • Terrestrial

    • Tundra

    • Taiga

    • Tropical Forest

    • Savanna

    • Desert

    • Temperate Grassland

    • Temperate Deciduous Forest


  • Arctic

  • Little precipitation: 15-25 cm/year

  • Average winter temp. -30 degrees C

  • Summer < 10 degrees C

  • Long winter; very short summer

  • Permafrost – almost permanently frozen snow/ice


Artic fox


  • Small plants with short roots, a few DWARF shrubs

  • Migratory animals or animals with High tolerance for very harsh conditions

  • Adaptations: Animals may have white fur for camouflage. Plants have short roots because of permafrost.


Polar bear


Taiga northern coniferous forest
Taiga (Northern Coniferous Forest)

  • Seasonal rainfall: 30-80 cm; some much more

  • Winters -50 degrees C in winter

  • Summer 20 degrees C

  • Long winter; short summer

Taiga northern coniferous forest1


Taiga (Northern Coniferous Forest)

  • Plants: cone-bearing trees, diverse shrubs, lichens & mosses

  • Animals: Migratory animals, large herbivores & predatory animals

  • Adaptations: Plants with waxy needles to help retain water. Animals may hibernate during coldest months



Timber wolves

Tropical rain forest
Tropical Rain Forest

  • Seasonal rainfall: 200-400 cm/yr

  • 25-29 degrees C year round

  • Located along the equator

    • Summer year round

Tropical forest



Tropical Forest

  • Most diverse species of plants & animals

  • Plants: Broad leaves, vines, orchids, bromeliads. Soil lacks nutrients

  • Animals: Lots of insects and tree dwellers

  • Adaptations: Many forms of camoflauge, bright colors, diet heavy on fruits

Boa constrictor

Poison Dart Frog




  • Seasonal rainfall; 50-120 cm/yr, with a long drought season

  • Temperature: 20-30 degrees C (warm!)

  • Distinct wet and dry seasons

  • Frequent fires during dry season




  • Plants: Tall grasses, scattered small trees and shrubs

  • Animals: Lots of herbivores (grazers), and carnivores (hunters)

  • Adaptations: Drought tolerant & fire-resistant






  • Rainfall < 25 cm/yr (arid/dry)

  • Hot deserts > 50 degrees C

  • Cold deserts (Antarctica) <-30 degrees C

  • Extreme changes in temperature

    • Ex: Very hot during the day & cold at night




  • Plants: Cacti, creosote bushes, succulents

  • Animals: small nocturnal carnivores, reptiles, birds & insects

  • Adaptations: Plants with deep roots and thick leaves to obtain and hold water. Reptiles with thick, waterproof skin to hold water. Many nocturnal animals.



Kangaroo Rat

Fennec Fox

Temperate grassland
Temperate Grassland

  • Dry winters, wet summers: 30-100 cm/yr.; seasonal drought

  • Cold winters < -10 degrees C; Hot summers 30 degrees C

  • Seasonal drought & periodic fires

  • Dark rich soil

Temperate grassland1

Blazing stars

Temperate Grassland

  • Plants: Lush grasses & wildflowers

  • Animals: Large herbivores & predators, burrowing mammals

  • Adaptations: Drought & fire-resistant plants.

Pronghorn antelope

Black-tailed prairie dog



Temperate deciduous forest
Temperate Deciduous Forest

  • Rainfall: 75-150 cm/yr

  • Cold Winters & hot summers. 0-35 degrees C

  • 4 distinct seasons

  • Our biome!

Temperate deciduous forest1


Temperate Deciduous Forest


  • Plants: Deciduous & coniferous trees, shrubs, mosses, ferns

  • Animals: variety of mammals, birds, insects

  • Adaptations: Deciduous trees lose their leaves in winter to keep from freezing. Some migratory animals & birds.






Types of interactions between organisms
Types of Interactions Between Organisms

  • Competition – when resources are scarce, only some organisms will survive

  • Food Chains & Webs – diagrams showing the feeding relationships in an ecosystem

  • Predator/Prey Relationship – some animals hunt others for food

  • Symbiotic Relationship – close interaction between two or more organisms of different species


  • When resources are limited, competition for those resources results.

    • Intraspecific competion – between organisms of the same species

    • Interspecific competition – between organisms of different species


  • Limiting Factor – any biotic or abiotic resource that limits the growth of an organism or population in a specific environment

    • Availability of water

    • Availability of food

    • Availability of habitat

    • Temperature


  • Density Dependent Limiting Factors – depend on the number of organisms in a population

    • Food, Water, Predation, Disease

  • Density Independent Limiting Factors – do Not depend on the number of organisms in a population

    • Weather, Natural Disasters, Human Activities


  • Habitat – the place where an organism lives

  • Niche – the role an organism plays in its environment

    • If two organisms occupy the same niche they will compete for resources until one species is forced out

Niche Partitioning for Warblers

Food chains webs
Food Chains & Webs

  • Producers (Autotrophs) – Produce their own food through Photosynthesis or Chemosynthesis

    • Ex: Plants, algae

  • Consumers (Heterotrohps) – Must consume other organisms for food & energy

Food chains webs1
Food Chains & Webs

Types of Consumers

  • Herbivores – Primary consumers

    • Eat Plants

  • Carnivores – Secondary & higher consumers

    • Eat other animals

  • Omnivores

    • Eat both plants and animals

Food chains webs2
Food Chains & Webs

Types of Consumers (continued)

  • Detritivores – Feed on organic waste (dead plants and animals)

    • Ex: Earthworms

  • Decomposers – Breakdown dead plants & animals into simpler molecules that can be absorbed

    • Ex: Bacteria, Fungi

Food chains webs3
Food Chains & Webs

  • The arrows in a food chain/web show the flow of energy from one organism to the next

  • Only 10% of the available energy is transferred from one trophic level to the next. The rest is lost as heat.

  • The Trophic Level of an organism is the position it holds in a food chain/web/pyramid

    • (Primary, Secondary, Tertiary, etc.)

Food chains webs4
Food Chains & Webs

  • Food Chain – a linear representation of energy transfer between organisms

Food chains webs5
Food Chains & Webs

  • Food Web – a network of interconnected food chains in an ecosystem

Food chains webs6
Food Chains & Webs

  • Food Pyramids

  • Pyramid of Energy – Shows the amount of energy available at each trophic level

  • Biomass Pyramid – Shows the amount of biomass at each trophic level

  • Pyramid of Numbers – Shows the number of individual organisms at each trophic level

Food chains webs7
Food Chains & Webs

Energy Pyramid

Pyramid of Numbers

Biomass Pyramid

Predator prey relationships
Predator/Prey Relationships

  • Predator populations can control the size of Prey populations, and vice versa.

  • The Top Predator in an ecosystem has no natural predators.

Symbiotic relationships
Symbiotic Relationships

  • Symbiosis – two organisms of different species living closely together.

  • There are 3 types of Symbiosis

    • Commensalism

    • Mutualism

    • Parasitism

Symbiotic relationships1
Symbiotic Relationships

  • Mutualism – Both species benefit

  • Commensalism – One species benefits and the other is not affected

  • Parasitism – One species benefits and the other is harmed (parasite & host)

Biological magnification
Biological Magnification

  • Chemicals or toxins may be introduced into an ecosystem through human actions.

  • As they move up through a food chain, they have a more severe affect on each higher trophic level.

  • Ex: DDT

Ecological succession
Ecological Succession

  • Ecological Succession – the predictable and orderly changes in the composition or structure of an ecological community over time.

    • Pioneer species – the first species to populate an area

    • Climax community – the final community of organisms in an ecosystem once it becomes stable

Ecological succession1
Ecological Succession

  • Primary Succession – occurs on surfaces where no soil exists

    • Ex: Volcanic rock surfaces after an eruption

Ecological succession2
Ecological Succession

  • Secondary Succession – occurs on pre-existing soil

    • Ex: A forrest after being burned or cleared for construction

Human impact on ecosystems
Human Impact on Ecosystems

  • Biodiversity is the variety of life in an ecosystem

  • It may be decreased by human activities such as:

    • Use of pesticides and chemical fertilizers

    • Deforestation and clearing land for construction

    • Introducing non-native species

    • Exploitation of wildlife