Unit 2 Ecology
Chapter 2 – Principles of Ecology
Chapter 2 Voc. Word List: Ecology, Biosphere, Abiotic Factors, Biotic Factors, Population, Community,
Ecosystem, Habitat, Niche, Symbiosis, Mutualism, Commensalism, Parasitism, Autotrophs, Heterotrophs,
Herbivores, Carnivores, Omnivores, Scavengers, Decomposers, Food Chain, Trophic level, Biomass, and Food
web
I.
Organisms & Their Environment
A. Ecology is the study of interactions between organisms and their environment
B. The biosphere is the portion of Earth that supports living things
 Living things are found everywhere – air, land, & water
Two factors involved in the biosphere
1. Abiotic factors – nonliving parts of an organism’s environment
a. Includes air currents, temperature, moisture, light, soil
2. Biotic factors – living organisms that inhabit an environment
b. Includes animals, plants, bacteria, etc.
c. organisms are dependent upon other organisms for food, reproduction, and shelter
C. Levels of organization –Remember the Hierarchy of Life Pyramid in Characteristics of Life
Notes Organism to Biosphere
1. Populations are groups of organisms of the same species
a. They compete for the same resources (food, water, mates, etc.)
b. Competition is high when resources are low; some species have adaptations to reduce
competition
2. Communities are made up of interacting populations in a certain area
a. Changes in one population may cause changes in another population
1) Ex.: If the population size of a predator increases, the population size of its
prey will decrease and vice versa
3. Ecosystems are made up of interacting populations in a community and the
community’s abiotic factors (main two-precipitation and temperature)
Two major types of Ecosystems
1) Terrestrial ecosystems are located on land (forests, meadows, rotting log)
2) Aquatic ecosystems are located in fresh and salt water (ponds, lakes, streams,
oceans)
3) Others may include places like the body, buildings, or food
D. Organisms in ecosystems
1. A habitat is a place where an organism lives
2. A niche is what a species does to survive in its environment (Its role in the ecosystem)
E. Survival relationships
1. Symbiosis is the close permanent relationship between different species
a. mutualism – when both species benefit from the relationship (ex. ants and acacia tree)
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b. commensalism – when one species benefits and the other is neither harmed or
benefited (ex. moss growing on trees)
c. parasitism – when one species benefits, but the other is harmed (ex. ticks on dogs)
1) Parasites do not usually kill the host as it would leave them without a food
source
2. Predators seek out and eat other organisms (prey)
II.
Nutrition and Energy Flow
A. How organisms obtain energy
1. Main source of energy is from the sun
2. Autotrophs (Producers) capture this energy to make food through photosynthesis
3. Heterotrophs (Consumers) cannot make their own food and must feed on other
organisms
a. Herbivores feed on plants (ex. grasshoppers, deer, rabbits)
b. Carnivores eat other heterotrophs (ex. lions)
c. Omnivores feed on both plants and animals (ex. humans, bears)
d. Scavengers feed on dead organisms; have beneficial role in ecosystem (ex. buzzards,
insects)
e. Decomposers break down and release nutrients from dead organisms (ex. bacteria)
1) Flow of matter and energy in ecosystem
a) Energy is trapped by autotrophs and used to make food (matter)
b) Matter and energy are passed through the ecosystem through
organisms’ consumption of food
c) A food chain shows how matter and energy move through an
ecosystem
Ex. berries  mice  black bear
a. Usually food chains consist of 2, 3, or 4 transfers
 Smallest is two organisms
b. Each organism represents a trophic level in ecological pyramids
2) There are three types of ecological pyramids: energy, numbers, and biomass
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Energy Pyramid
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Biomass Pyramid
Number Pyramid
a.) Biomass is the total amount of organic matter present in a
trophic level; is potential food for the next level
b.) Only 10% is transferred from one level to the next
3)
4)
5)
6)
7)
Autotrophs make up 1st level
1st order heterotroph (2nd level) – feeds on plants
2nd order heterotroph (3rd level) – feeds on 1st order heterotrophs
3rd order heterotroph (4th level) – feeds on 2nd order heterotrophs
Some organisms may feed at different levels
c. A food web shows all possible feeding relationships at each trophic level in a
community
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Cycles in Nature
Matter is never lost; it is recycled
1. In the water cycle, water is cycled through evaporation and condensation Carbon is a fundamental
element in the molecules of life (proteins, carbohydrates, fats)
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2. It circulates through the carbon cycle primarily by respiration and photosynthesis, as well as by
combustion and decay.
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3. Nitrogen is a necessary element that is circulated by the nitrogen cycle.
 Nitrogen gas from the air is converted into a usable form for plants by bacteria on the roots of
legumes
 It is released through waste products and decay.
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4. Phosphorus is cycled in two ways-organic and inorganic
 Animals obtain phosphorus by eating plants. When they die, the phosphorus returns to the soil
 Phosphorus is contained in rocks. When the rocks erode, phosphorus is returned to the ecological
system.
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Chapter 3 – Communities and Biomes
Chapter 3 Voc. Word List: Limiting factors, Tolerance, Primary succession, Pioneer species, Climax
Community, Secondary succession, Biome, Photic Zone, Aphotic Zone, Estuaries, and Intertidal Zone
I.
Communities
A. Limiting factors- Any biotic or abiotic factors that restrict the survival of an organism
 May include water, food, predators, temperature/climate
 Tolerance is an organism’s ability to withstand fluctuations in environmental factors
B. Succession- Refers to natural changes that occur in an ecosystem over time
 Occurs in stages
Two main types
 Primary succession – colonization of barren land by communities of
organisms
 Ex.: After a volcano, the cool lava has no living organisms
 The first inhabitants (pioneer species) are usually lichens
 These help to make soil from the rock so plants can take hold
 A climax community is stable and mature and undergoes little change
 Secondary succession – series of changes that occur after an existing
community is disrupted, such as after a forest fire
C. Biomes-Are major types of ecosystems with distinctive temperatures, rainfall, and organisms
Two major types
1.Aquatic biomes
 Marine biomes
 Water is saline-salty
 Photic zone – is shallow enough for sunlight to penetrate; contains
plant-life or phytoplankton
 Aphotic zone – do not receive sunlight; deepest part of ocean
 Estuaries contain mixed salt and fresh water and are found where
rivers meet the ocean
 The intertidal zone is the portion of the shoreline that lies between
the high and low tide lines
May vary from place to place, but receives high levels of
sunlight, nutrients, and oxygen
 Freshwater biomes include ponds, lakes, streams, rivers
2.Terrestrial biomes
 Climate is determined by latitudinal location on Earth
I. The tundra is the coldest land biome
1. Arctic tundra- Most are found at latitudes greater than 55 to
60 North degrees on the coastal plains in the arctic regions
of Siberia, northern Europe, Canada, and Alaska
a. Known as a cold desert- cold with the least amount of
rainfall of any biome
b. Form in areas where temperatures are continuously too
low to produce photosynthesis (below 19.4oF (-7oC))
and long periods of low light or darkness
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II.
III.
IV.
V.
VI.
c. Others factors that cause tundra areas: strong winds,
abrasion (type of wind erosion), and low precipitation
d. Underneath the top layer of soil is the permafrost,
which is permanently frozen
e. Short growing season
2. Alpine tundra-Worldwide in high elevations (mountainous
and hilly areas) including at the equator
a. More rain than the Arctic tundra
b. Many have different types of glaciers
c. Some areas have permafrost in patches
The taiga (coniferous or boreal forest) is south of the tundra
o Is warmer and wetter than tundra
o Has mostly trees with needles (such as Black Spruce trees)
The desert is the driest biome (with the exception of Arctic tundra)
with little plant-life
o Animals are adapted to extreme temperatures and little rainfall
The grasslands have rich soil and grasses
The temperate forest (deciduous forest) is dominated by hardwood
trees that lose their leaves annually
The Rain forest
1. Temperate Rainforest are located in areas with lots of rain
but cooler temperatures than Tropical Rain forest
a. 2/3 are found in the Pacific Northwest by the
Coastal mountain range in Washington, Oregon,
and northern California
i. Also located in Canada and parts of Alaska
b. Rich soil
c. No poisonous snakes
2. Tropical Rain forest are located near the equator
o Has warm, wet weather
o Has the more diversity of species than any other biome
on Earth
o Poor soil
o Lots of poisonous snakes
Chapter 4 – Population Biology
Chapter 4 Voc. Word List: Exponential growth, Carrying Capacity, Population density, Density –dependent
factors, Density-independent factors, Demography, and Population Growth rate
I.
Population Dynamics
A. When populations are growing, they exhibit exponential growth
(SEE P. 92, FIG. 4.2)
1. As the population gets larger, it grows at a faster rate
2. This population growth cannot continue indefinitely
a. Limiting factors slow growth: food availability, predators, lack of space, disease
b. The population growth stabilizes; deaths will begin to exceed births
c. Population number will fall to a level that the environment can support (carrying
capacity) (SEE P. 93, FIG. 4.3)
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B. Some organisms (such as mosquitoes) undergo rapid population growth, which declines when
conditions become unfavorable
C. Some organisms (such as elephants) have long lives and tend to maintain population sizes at
carrying capacity
D. Population density refers to the number of individuals in a particular area
1. Organisms can show three patterns of dispersal: random, clumped, uniform
2. Density-dependent factors are limiting factors that have a greater effect as the
population increases
a. Include disease, competition, predators, parasites, food
3. Density-independent factors are limiting factors that affect population size regardless of
the density
a. Include storms, floods, drought, habitat disruption
II.
Human Populations
A. Human population growth has been rapid since around 1800 due to technological advances
1. Improved medical care/disease prevention
2. Increased food production
3. Improved water treatment
B. Demography is the study of human population size, density and distribution, movement, and
birth/death rates (SEE P. 103, FIG. 4.11)
1. Is based upon information from the census
2. Can provide information about a country’s economic and social future
C. Population growth rate is determined by subtracting the death rate per 1000 individuals from the
birth rate per 1000 individuals
1. If the birth rate equals the death rate, population growth is zero
Chapter 5 – Biological Diversity/Conservation
Chapter 5 Vocabulary Word List: Biodiversity, Extinction, Endangered species, Threatened species, Habitat
loss, Habitat fermentation, Habitat degradation, Acid precipitation, Conservative Biology, Habitat Corridors,
Sustainable resources, and Capacity
I.
Biodiversity
A. Biodiversity refers to the variety of species within a given area
1. Ex. One hectare of a cornfield has less biodiversity than one hectare of a rain forest
2. Will differ from place to place on the Earth
B. The higher the biodiversity, the more stable an ecosystem
1. The loss of one species will not have as great an impact
C. Extinction occurs when all members of a species have died
1. Some extinction occurs naturally
2. It is believed that human interference accounts for the increased rates of extinction that
are occurring
3. A species is considered to be endangered when its numbers become so low that
extinction is possible
4. A species is considered to be threatened when it is likely to become endangered
D. Threats to biodiversity
1. Habitat loss
a. Ex. rain forest, coral reef
2. Habitat fragmentation is the separation of wilderness areas from other wilderness areas
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3. Habitat degradation is damage to a habitat by pollution
a. Acid precipitation – has low pH due to sulfur dioxides and nitrogen oxide
combine with water vapor; damages plants, soil, lakes
b. Water pollution – degrades aquatic environments; caused by runoff of fertilizers,
animal wastes, detergents, and chemicals, as well as trash
c. Land pollution – caused by trash, pesticides, and chemicals
4. Introduction of exotic species (nonnative)
a. May lead to loss of other species
II. Conservation of Biodiversity
A. Conservation biology – study and implementation of methods to protect biodiversity
1. Based on ecological principles of conserving species and natural resources
B. Several methods have been implemented
1. U.S. Endangered Species Act (1973) made it illegal to harm endangered or threatened
species or its habitat
2. National parks (Yellowstone, Sequoia, etc.) have been established to preserve habitats
and communities
3. Habitat corridors allow migration organisms from one wilderness area to another
4. Sustainable resources are natural resources that people use that benefit both them and
the ecosystem
5. Reintroduction programs involve releasing organisms into area where they once lived
6. Some plant and animal species exist in only captivity
o They may be reintroduced over time, which may be difficult
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