Ecosystems Chapters 55 & 56

Ecosystems All abiotic factors & species

▼ A desert spring ecosystem ecosystems ◀ An island ecosystem ▼ A desert spring ecosystem Figure 55.2 Ecosystems at different scales

Ecosystems Processes in the ecosystems 1. Energy Comes from sun Photosynthesis(chemical energy) 2. Biogeochemical cycles(nutrients) Chemicals that move through ecosystems Mostly found in nonliving reservoirs

Microorganisms and other detritivores Sun Key Chemical cycling Energy flow Loss of heat Primary producers Primary consumers Detritus Figure 55.4 An overview of energy and nutrient dynamics in an ecosystem Microorganisms and other detritivores Secondary and tertiary consumers

Ecosystems Photosynthesis Decomposition & respiration return elements to abiotic forms Elements are recycled Energy is released as heat Sun continuously supplies energy Evaporation & precipitation circulate elements

Trophic levels Energy flow through the ecosystem Autotrophs: primary producers Heterotrophs: consumers Primary consumers: herbivores Secondary consumers: carnivores Decomposers: break down organic matter Detritivore: live on refuse of ecosystem

Trophic levels “trophos” means feeder All levels feed on another Food chain Represents these levels Food web: More complex relationships between levels

Figure 55.1 How can a fox transform a grassland into tundra?

Figure 55. 1a How can a fox transform a grassland into tundra Figure 55.1a How can a fox transform a grassland into tundra? (part 1: fox with seabird)

▼ Fungi decomposing a dead tree Decomposers ▼ Fungi decomposing a dead tree Figure 55.3 Detritivores ▲ Rod-shaped and spherical bacteria in compost (colorized SEM)

Food chain

Food chain

Food web

Energy flow Primary productivity: Amount of energy produced by photosynthesis (organic matter) in a community Biomass: Total mass of organisms in an ecosystem Rainforests or wet lands have a high productivity

Energy flow Secondary productivity Rate of biomass of heterotrophs Less than primary due to 1. Not all plants are consumed by herbivores 2. Some energy of herbivores is passed as waste 3. Some energy is lost as heat

Energy flow

Energy flow Gross primary production (GPP) Amount light energy converted to chemical energy over time Net primary production (NPP) GPP less the amount of energy for plant cellular respiration (R) NPP= GPP-R

1 2 3 Net primary production (kg carbon/m2·yr) · Energy flow Figure 55.6 Global net primary production in 2002 Net primary production (kg carbon/m2·yr) · 1 2 3

Energy flow in food chains Ecological pyramids Relationship of energy, biomass or numbers in an ecosystem The limit is based on amount of sunlight and nutrients available

Ecological pyramids

Ecological pyramids

Ecological pyramids

Ecological pyramids

Water cycle Oceans cover ¾ of earth’s surface Sun powers evaporation of water from oceans 90% of water in atmosphere over land comes from plant transpiration Most falls over the ocean as rain 2% is frozen in ice Water supplies the hydrogen in ATP formation

Water cycle

Carbon cycle Photosynthesis uses up about 10% of atmospheric CO2 Respiration replaces CO2 in the air Most CO2 is in fossil fuels, coals, gas Use of these is increasing CO2 in the atmosphere

Carbon cycle

Nitrogen cycle Prokayotes “fix” nitrogen to usable form Nitrogen is being added to the system by fertilizers

Nitrogen cycle

Phosphorus cycle Exist in mineral form (not atmosphere) Need for ATP, phospholipids, DNA, RNA Fertilizers adding a lot

Phosphorus cycle

Ecosystem stabilization More diverse species (species richness) 1. Ecosystem productivity 2. Spatial heterogencity More habitat variation (soils, topography) allows more areas for animals to live 3. Climate More stable the weather the greater the species

Biodiversity hotspots

Biodiversity

Biodiversity 1. Genetic diversity 2. Species diversity 3. Ecosystem diversity

Threats to Biodiversity Habitat loss Introduced species Overexploitation

Problems Pollution Rhine river (Mercury, pesticides 1986) DDT (chlorinated hydrocarbons) Absorbed in animal fats Biological magnification: Become more concentrated in food chain

DDT

Acid rain Sulfur dioxide Forms sulfuric acid when comes with rain Lowers pH Kills wildlife

Acid rain

Farming

Ozone layer Protects against UV Thinning 1975 Chloroflurocarbons (CFC’s) Increased melanoma

Ozone

Ozone

Greenhouse effect Increased carbon dioxide & other gases Reflects heat from earth Keeping it in the atmosphere Global warming

Greenhouse effect

Effect of warming Plants/animals further north Migratory changes Species have problems adapting Increasing sea level Retreating glaciers More severe weather changes

Logging

Conservation Conservation Biology: Attempts to conserve biodiversity Restoration Ecology: Return ecosystems to natural state