Ecosystems

5.1 and 5.3

Ecosystems

• All life on Earth is interconnected– Populations with other populations– Populations with nonliving environment

Vocabulary Check• Species- a group of organisms that can breed and

produce fertile offspring.• Habitat- where the species normally lives• Population- a group of organisms of the same

species• Community- a group of populations (can be diff.

species)• Ecosystem- a community and its abiotic environment• Ecology- study of relationships between living

organisms and their environment

Abiotic Factors

• Abiotic- Nonliving factors that affect distribution of organisms.– Temperature range– Availability of water– Amount and quality of sunlight– Physical structure– pH and composition of soil– Abiotic catastrophes (fires, avalanches,

floods)

Abiotic Factors

• Animals adapt to the abiotic and biotic factors of an environment.

• Adaptation to one ecosystem usually means exclusion from another.

Food Webs and Energy

• Review:– Autotrophs- producers- energy from non-living

sources– Heterotrophs- consumers and decomposers

• Energy from living sources– Herbivores- primary consumers (eat plants)– Carnivores- secondary consumers (eat

herbivores)– Decomposers- consume organic wastes and

dead organisms.

Decomposers

• Saprotrophs: live on or in non-living organic matter– Secrete enzymes to digest and then reabsorb

nutrients– Fungus and Some Bacteria

• Detritivores: Organisms that eat non-living organic matter– Examples: Earthworms, woodlice, bottom feeders in

rivers

Food Webs and Energy• 10% rule- each level of the food pyramid receives

10% of the energy from the level below it.

Hawk (.4 kJ m-2 y-1)Snakes (4 kJ m-2 y-1)Herbivores (40 kJ m-2 y-1)Grasses (400 kJ m-2 y-1)(Notice the units)

Hawks need to eat a lot more to get the energy they need

Food Web and Energy

• Biomass- the total quantity of living matter at each trophic level.

• Just like available energy decreases, so does biomass at each level.

Population Dynamics

• Two types of population growth– Exponential- growth under ideal conditions. Will result

in enormous numbers of individuals.– Logistic- At first grows normally but slows down as

competition and other factors limit reproduction and survival.

Carrying capacity

• The largest population of a species that the environment can support. – Are not stable– Invention of fertilizers led to more crops which

led to more humans. The increase in crops could support a higher carrying capacity for humans.

Phases of Population curve

(Plateau phase)Part 3 (transitional phase)Part 2

Part 1 (exponential growth phase)

Factors that affect population size

• Natality- # of new members (births)• Mortality- # of deaths• Immigration- # of members arriving• Emigration- # of members leaving

Limiting Factors

• Factors that limit productivity in an ecosystem– Availability of resources- light, water, shelter,

oxygen– Build up of waste, excrement or Carbon

dioxide– Predation– Disease

Carbon Cycle

• Carbon is constantly recycled in the environment

• Picture is worth more

Greenhouse Effects

• The trapping of heat by the Earth's atmosphere. (CO2, H2O etc.).

Carbon Dioxide Levels

• Prior 1850 - 274 ppm 1958 - 316 ppm 1992 - 351 ppm

• Point: the levels of CO2 are rising. The cause is probably due to humans.

Causes of CO2 rise

• Industrialization.• Burning of fossil fuels.• Loss of forests.

Result

• Earth will heat up. • Ice caps melt and sea levels will rise.• Climate shifts.• Increased Ps (?)

Enhanced Greenhouse effect

• The “not natural” greenhouse effect- caused by humans

1. Sunlight enters atmosphere2. Reflects off Earth goes back to atm3. Some light turned to heat4. Greenhouse gases retain heat and trap it5. Earth’s atm is warmer than space

Greenhouse gases

• Carbon dioxide• Methane:

– Cattle ranching– Waste disposal in landfills– Production and distribution of natural gas

Conclusions from IPCC in 2007

• Global temps are increasing• 90% chance this is due to human activity• Next 100 years, sea level will rise 18-59

cm• Severe weather events will increase

Precautionary principle

• Ethical theory that states action should be taken to prevent harm– Even if there is not sufficient data to prove

that activities will have negative consequences

– If companies wish to engage in activities, they must prove that it will do no harm

Conclusion

• Prevention is better than a cure later

Arctic systems

• More and more ice is melting every year• Less snow and more frozen rain• Some regions now population with

mosquitoes• Woody shrubs are appearing where there

used to be only moss• Bird species are moving north