Biology i comp 3 review
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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

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Biology IComp 3 Review

Organisms and Their Environments

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

  • 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

  • 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

Water 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

Carbon 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 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

Nitrogen Cycle

Levels of Organization

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







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 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 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)

  • 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 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

  • Seasonal rainfall: 200-400 cm/yr

  • 25-29 degrees C year round

  • Located along the equator

    • Summer year round



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

  • 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

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

  • Rainfall: 75-150 cm/yr

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

  • 4 distinct seasons

  • Our biome!


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

  • 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

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

    • Ex: Plants, algae

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

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 & 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 & 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 & Webs

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

Food Chains & Webs

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

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 & Webs

Energy Pyramid

Pyramid of Numbers

Biomass Pyramid

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

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

  • There are 3 types of Symbiosis

    • Commensalism

    • Mutualism

    • Parasitism

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

  • 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 – 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 Succession

  • Primary Succession – occurs on surfaces where no soil exists

    • Ex: Volcanic rock surfaces after an eruption

Ecological Succession

  • Secondary Succession – occurs on pre-existing soil

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

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

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