Ecology
Chapters 2-5
Organisms and their
environments
Chapter 2
What is ecology?


Study of interactions among organisms and
their environments
Includes relationships between living and
nonliving
Aspects of ecology
Biosphere



Portion of the Earth that supports life
Extends from high in the atmosphere to the
bottoms of the oceans
Thin, but diverse
Abiotic factors



Nonliving parts of the environment
Air currents, temperature, moisture, light,
soil
Determine which species can live in an
area
Biotic factors


Living parts of the environment
All organisms inhabiting an environment
Levels of organization
Dependence on others for food,
shelter, reproduction, or protection
Species

A group of organisms that can interbreed
and produce fertile offspring
Population


All organisms of the same species
inhabiting a certain area
May compete for food, water, or other
resources

Some species have adaptations that
decrease competition


Different forms during development  frogs
Different colors for closely related species 
cichlid fish
Community


Collection of interacting populations in a
certain area
Changes in one population causes changes
in others
Ecosystems



Interactions of biotic and abiotic factors in
a certain area
Terrestrial, freshwater, marine
Energy flows between populations and the
environment  self-sustaining
Organisms in ecosystems
Habitat


Place where an organism lives
Contains organisms of different species
Niche



Role and position of species in an
environment
How it meets it’s needs  food, shelter,
reproduction
Includes interactions with biotic and abiotic
factors
Niche cont.



One species = one niche
Advantageous  decrease in competition
Competition arises with overlapping niches
Predator/prey relationships


Predators are carnivores and omnivores
Prey are herbivores
Symbiosis
Relationships in which there exists a
close association among organisms of
different species
Commensalism


One species benefits and the other neither
benefits or is harmed
Sharks and pilot fish
Mutualism



Both species benefit
Ants and acacia trees
Humans and bacteria
Parasitism



One species benefits and the other is
harmed
Dogs and fleas
Humans and tapeworms
Nutrition and energy flow
How organisms obtain energy
Autotrophs  producers

Use energy to synthesize their own
nutrients
Phototrophs  use energy from the sun
Chemotrophs  use energy from chemical
compounds
Heterotrophs  consumers

Obtain energy and nutrients from the
environment
Herbivores  plants only
Carnivores  animals only
Omnivores  both plants and animals
Scavengers  carrion and refuse (clean-up)
Decomposers  break down dead and decaying
organic matter (recycle nutrients)
Matter and energy flow
Food chains  patterns of flow

The arrows indicate the direction of energy
flow

Grass  Mouse  Owl


Energy is lost at each level in the form of
heat  food chains only have up to 5
levels
Levels are called trophic levels
Food webs  represent all
possible feeding relationships


Made of overlapping food chains
More realistic  most organisms depend
on more than one species for food
Ecological pyramids



Show relative amounts of energy or matter
by trophic level
Initial source of energy is the sun
10% rule  only 10% of the available
energy is passed from one trophic level to
the next
Natural cycles
Recycling of matter and energy
Water cycle  pattern of water
movement
Carbon cycle
Nitrogen cycle
Communities
Chapter 3
Living in the community
Limiting factors


Biotic or abiotic factors that restrict
numbers, reproduction, or distribution of
organisms
Through interdependence, factors that limit
organisms populations may have an
indirect effect on another
Limiting factors cont.






Food availability
Predators
Moisture
Soil pH
Sunlight
Temperature
Ranges of tolerance


Ability to withstand fluctuations in limiting
factors
Varies between species and individuals
Succession
Natural changes and species
replacements taking place in an
ecosystem
Occurs in stages

May take decades or centuries
Primary succession  new sites

Pioneer species  first to arrive



Colonize bare rock  turns to soil
Lichens and mosses
Thin soil allows grasses  soil gets deeper
Primary succession cont.



Grasses give way to shrubs  deeper soil
Eventually trees can colonize
Climax community  stable, mature
community that changes little

Disrupted only by natural disasters
Secondary succession


Soil present
Sites devastated by natural disasters or
human intervention



Faster than primary
Pioneer species are different
Can also happen to ponds
Biomes
Large groups of ecosystems sharing
the same type of climax communities
Biomes Webquest

http://www.angelfire.com/moon/may3/bio
meswebquest.html
Aquatic biomes
Marine and freshwater (75%)
Marine biome  97% (largest)


Contains largest amounts of biomass 
plankton
Most stable (unchanging) biome
Freshwater biome  3%

Lakes  only top few feet warmed by sun



Limiting factor
Decomposers at bottom recycle nutrients
Running water contains more O2
Estuaries



Mixing of fresh and saltwater
Salinity changes with tide  increases
biodiversity
Used as breeding grounds by many species
Terrestrial biomes
Tundra




Circles the poles, tops of mountains
Treeless  thin soil supports only grasses
and shrubs
Cold temperatures slow decay  slow
nutrient recycling
Short growing season  limiting factor

Permafrost  permanently frozen ground
Taiga (coniferous forest)


Just south of the tundra
Cone-bearing trees




Pine, fir, hemlock, and spruce
Warmer and wetter than the tundra
Harsh winters, short and mild summers
No permafrost
Desert  driest


Sparse plant life
Plant adaptations:




Spines instead of leaves
Extensive root systems
Rapid growth and development
Thick tissue  water conservation
Grassland  interior of
continents




Not enough rainfall to support trees
Includes prairies, steppes, and savannas
Largest terrestrial biome
Breadbaskets  fertile soil
Temperate deciduous forest




We live here!
Broad-leaved hardwood trees that lose their
leaves annually
Soil composed of top layer (humus) and
bottom layer (clay)
More rainfall than taiga
Tropical rainforest


Warm, wet, constant temperature and
humidity
Highest in biodiversity



Year-round growing conditions
Multitude of possible habitats
Soil poor in nutrients  quickly absorbed
by plants
Population biology
Chapter 4
Principles of population growth

Population growth  increase in size of
population over time
Not linear  J-shaped curve
Exponential growth

As population increases, growth rate
increases

Initial growth is slow due to small number of
reproducing organisms
Principles cont.

Limiting factors eventually stop growth


Food supply
Living space
Carrying capacity

Number of organisms of 1 species the
environment can support



Under  births exceed deaths
Over  deaths exceed births
Would be infinite without limiting factors
Patterns of reproductive growth
Depend on environmental conditions
Unpredictable environments 
rapid life histories





Small body size
Rapid growth and development
Early reproduction
Short life-span
Mice
Stable environments  slower





Large body size
Slow growth and development
Reproduce slowly
Long life-span
Sea turtles
Environmental limits
Density-dependent factors




Increased effects as population size
increases
Disease
Competition
Parasites
Density-independent factors




Not related to population size
Temperature
Droughts
Storms
Organism interactions limit
population size
Predation


Both predator and prey populations show a
cycle of increases and decreases over time
Cuts down on competition for resources
Effects of crowding and stress


Competition causes stress
Results:




Aggression
Decreased parental care
Decreased fertility
Decreased resistance to disease
Human population growth
Demography


Study of human population growth
characteristics
Growth rate, age structure, geographic
distribution


Has been increasing exponentially over the
last few hundred years
Elimination of competition, increased food
supply, disease control
Effects of birthrates and death
rates


Growth = birthrate – death rate
Can provide clues to a country’s growth
Effects of age structure


Rapid growth  higher number of younger
people
China vs. Japan
Effects of mobility



Immigration  moving into a population
Emigration  moving out of a population
No effect of world population
Population Growth Mini-Lab



Textbook pg. 105
Please complete Mini-Lab 4-2 on a
separate sheet of paper
Hand in by the end of the period
Biological Diversity and
Conservation
Chapter 5
Biodiversity  variety of life in
an area


Tropical regions  2/3 of all land species
Important due to species interdependence




Effects on 1 population cascade to others
Predator-prey relationships
Symbiotic relationships
Biodiversity brings stability
Biodiversity cont.





Important to humans
Plants cycle O2 and CO2
Diverse diet
Provides basis for new species of
agriculture
Improve health  digitalis and other
medicines
Loss of biodiversity
Threatened species


Population size is decreasing rapidly
African elephant, loggerhead turtles
Endangered species


Population size is so low that extinction is
possible
Florida manatees, California condors,
peregrine falcon
Extinction



Disappearance of a species
Due to natural processes and human
activity
Passenger pigeon, dodo
Threats to biodiversity
Habitat loss



Razing forests for agriculture or
construction
Mining coral reefs for building materials or
jewelry
Overgrazing land
Habitat fragmentation



Separation of wilderness areas from other
wilderness areas
Like islands  lose biodiversity due to
isolation
Clearing land or building roads
Biotic issues


Not enough food for large predators 
migration
Often species can’t reestablish themselves
Abiotic issues


Can change climate
Dust Bowl in Oklahoma
Habitat degradation
Damage by pollution
Global warming



Increase in global temperature due to high
atmospheric CO2 levels
Pollution and overpopulation
Gradual melting of polar ice caps and
change in global climate
Acid rain




Precipitation with low pH
Sulfur and nitrogen from industry combine
with atmospheric water vapor to form
sulfuric and nitric acids
Damages plant tissues
Changes acidity of soil and lakes
Chlorofluorocarbons  CFCs


Break down ozone layer
Gradual increase in damaging solar
radiation
Fertilizers and animal wastes



Washed into large bodies of water by
runoff
Cause algal blooms
Destruction of coral reefs
Solid wastes



Landfills
Take up space
Pollute soil and ground water
Pesticides


Get into the food chain and harm other
animals
DDT and the American bald eagle
Introduction of exotic species



No natural predators
Out-compete native species
Zebra mussels, purple loosestrife
Strategies of conservation
biology
Legal protection of species

Endangered Species Act  1973


Prohibits trade of endangered or threatened
species
Clean Water/Air Acts
Preserving habitats


Nature preserves and national parks
Habitat corridors  strips of protected land
used by migratory animals
Reintroduction programs


Release organisms into areas where the
species once lived
Not always successful



Expensive
Animals become domesticated
Gray wolf
Captivity


Permanent  zoos
Temporary  rehabilitation centers (Sea
World)