ecology chapters 2-4 ecology is the study of interactions that take place between organisms and...
Post on 20-Jan-2016
215 Views
Preview:
TRANSCRIPT
EcologyChapters 2-4
•Ecology is the study of interactions that take place between organisms and their environment
• The nonliving parts of an environment are the abiotic factors.–air currents, temperature, moisture, light, and soil.
The nonliving environment: Abiotic factorsThe nonliving environment: Abiotic factors• This graph shows how the plant’s glucose
(food) production is affected by temperature.
5
10
15Food Production in Salt Bush
10 20 30 40 50Temperature (°C)
Food
pro
duct
ion
(mg
of g
luco
se/h
r)
•All the living organisms that inhabit an environment are called biotic factors
I. Levels of Organization
• A population is a group of organisms of the same species which live in the same area.
Levels of Organization
• A community is made up of interacting populations
Levels of Organization
• An ecosystem is a community plus the abiotic components of that area.
• A habitat is the place where an organism lives out its life.
• A niche is the role or position a species has in its environment—how it meets its specific needs
Symbiotic relationships
• Mutualism: both benefit– E. coli in digestive tract– In termite’s guts– In grazer’s guts– In flashlight fish
• Commensalism: one benefits, other unaffected (rare)– Orchids on trees
• Parasitism: one benefits (parasite), one hurt (host)– Pathogenic bacteria, (make you sick)
II. Energy Flow
• The ultimate source of the energy for life is the sun.– Utilized by
producers (autotrophs) in photosynthesis
• Consumers are heterotrophs– Herbivores: eat producers– Carnivores: eat other consumers– Omnivores: eat both plants and
animals– Scavengers: eat food already dead– Decomposers: absorb nutrients
from decaying organisms
Herbivores: eat producers
Carnivores: Eat other consumers
Scavengers: eat dead animals
Decomposers: absorb decaying organisms
Energy Flow
• A food chain shows how matter and energy move through an ecosystem
• Berries mice snake• Each organism in a food chain
represents a feeding step, or trophic level
• Available energy decreases with each trophic level
•Some lost as feces•Some lost in cellular respiration as
heat•Only 10% passed on
Energy and trophic levels: Ecological pyramidsEnergy and trophic levels: Ecological pyramids
• The pyramid of energy: available energy decreases at each succeeding trophic level.
Pyramid of Energy
Heat
Heat
Heat
Heat
0.1% Consumers
1% Consumers
10% Consumers
100% Producers
Parasites, scavengers, and
decomposers feed at each
level.
Cycles in Nature
• Energy flows, it does NOT cycle• Water cycle
– Evaporation condensation precipitation
• Carbon Cycle– Photosynthesis fixes atmospheric CO2 into living
matter
– Respiration by organisms returns CO2 to atmosphere
– Carbon in dead organisms returns to atmospheric CO2 through combustion or decomposer respiration
Cycles in Nature
• Nitrogen Cycle
• Phosphorus Cycle
IV. Population Growth
• The graph of a growing population starts out slowly, then begins to resemble a J-shaped curve.
How fast do populations grow?How fast do populations grow?Population Growth of Houseflies
1 million
500,000
100One year
Pop
ula
tion
siz
e
• A limiting factor restricts the existence, numbers, reproduction, or distribution of organisms.
Common Limiting Factors
Sunlight
ClimateAtmospheric gases
Temperature
WaterNutrients/Food
FireSoil chemistrySpaceOther organisms
Limiting factorsLimiting factors
• Limiting factors may cause population growth to slow and stabilize in an S-shaped growth curve.
What can limit growth?What can limit growth?Characteristics of Population Growth
Exponential growth
Carrying capacity
J curve S curve
Pop
ula
tion
Time0
DIS
EA
SE
SPA
CE
PR
ED
A-
TO
RS
FO
OD
Carrying Capacity (K)
• The number of organisms of one species that an environment can support
Predation affects population sizePredation affects population size• The data in this graph reflect the number of
hare and lynx pelts sold to the Hudson’s Bay Company in northern Canada from 1845 through 1935.
Lynx and Hare Pelts Sold to the Hudson’s Bay Company
Num
ber
of o
rgan
ism
s(in
tho
usan
ds)
Times (in years)
LynxHare
VI. Life History Strategies• R Strategy: (Rapid)
– small body size– mature rapidly– short life span– Live in a changeable or
unpredictable environment– Large “litter”– Little to no parental care– Tend to overshoot carrying
capacity before falling back to carrying capacity
Life History Strategies
• K Strategy:
– Large body
– Mature slowly
– Long-lived
– live in stable environments
– Few, well cared for young
– Population maintained at or near K
Types of Limiting Factors
• Density Dependent factors– Increased effect as population size increases
• Disease• Competition• Food
• Density Independent Factors– Affect population regardless of size
• Storms• Floods• pollution
V. Competition
• Gause (1934) hypothesized that two species with the same niche requirements cannot live together– Tested with paramecium– Grown separately, both species reach K– Grown together, one reaches K, the other
becomes extinct
•Competitive exclusion principle
VII. Biodiversity
• Def: the variety of species in a specific area– Ex. Cornfield has less biodiversity than equal
area of rainforest
• Increases as you near the equator– Hectare of Amazon rainforest ~300 tree species– Hectare of temperate deciduous forest ~30
tree species
• Increases with increasing primary productivity– Supports more “links” in food chain due to
higher energy base
Importance of Biodiversity
• Beauty• Interdependence of nature
– Food chain links– Symbiotic relationships– Abiotic changes as the result of species loss– Resources for humans
• Genetic – to produce new food varieties• Medical – quinine, cyclosporine, penicillin• Raw materials
Rosy periwinkle, the source of drugs for Hodgkin’s disease and leukemia
Invasive (Exotic) Species
• Def: species that are not native (introduced) to a community– Ex. Goats on Santa Catalina Island– Ex. Sea lamprey in Great Lakes
• Population grows exponentially at first due to absence of predators and ability to outcompete native species
• May drive native species to extinction
top related