Ecosystems Chapter 3

ECOLOGY The study of how organisms interact with one another and their environment

Cells Prokaryote One-celled organism Lacks a nucleus Lacks internal membrane structures Example – bacteria Eukaryote Distinct nucleus Contain organelles with membranes

Cells

Species Definition: set of individuals that produce fertile offspring Nomenclature system – Page S46 in text How many? Best guess is 10 – 14 x x 10 6 identified

Connections in Nature Population Group of individuals of same species living in same place at same time There is genetic diversity (variation) A habitat is a place where an individual or population lives; a supply of resources

Connections in Nature Community Definition: All the populations of different species living in a certain place Interaction occurs! This includes feeding, competition for other resources

Connections in Nature Ecosystem Definition: A community of different species interacting with each other and their non- living environment Huge range in sizes Natural or artificial No clear boundaries (erosion, winds, migration, etc)

Connections in Nature Biospheres Definition: parts of the earth, air, water and soil where life is found A global ecosystem

Fig. 3-3, p. 52 Parts of the earth's air, water, and soil where life is found Biosphere Smallest unit of a chemical element that exhibits its chemical properties Ecosystem Community Population Organism A community of different species interacting with one another and with their nonliving environment of matter and energy Populations of different species living in a particular place, and potentially interacting with each other A group of individuals of the same species living in a particular place Cell An individual living being The fundamental structural and functional unit of life Molecule Atom Chemical combination of two or more atoms of the same or different elements

KEEPING US ALIVE

Components of Life Support Atmosphere Troposphere: closest to surface of the earth (7-11 km thick); Majority of air is here (78% N 2, 21% O 2, 1% CO 2, H 2 O, CH 4 – greenhouse gases!)

Components of Life Support Atmosphere Stratosphere: next closest layer, rides on top of troposhphere Most of atmospheric O 3 is found here Ozone absorbs most of the sun’s UV radiation

Components of Life Support Hydrosphere Consists of all water on or near the surface of the earth May be in liquid form May be in solid form (ice caps, permafrost, etc.) May be in vapor form

Components of Life Support Geosphere Consists of the: Core: liquid and solid; produces magnetic field Mantle: semi-molten state; largest portion of the geosphere Crust: hard, outermost shell; all our resources are here

Components of Life Support Biosphere Parts of the atmosphere, geosphere, and hydrosphere where life exists Extends from about 9 km up to the bottom of the ocean

Land and Water Biomes ‘Biome’ only applies to terrestrial portions of the biosphere A biome will have a distinct climate A biome will have a distinct set of species

Land and Water Aquatic Life Zones Includes freshwater and ocean (marine) life zones

Factors Sustaining Life One-way flow of high quality energy Originates from the sun Travels through organisms Is dissipated into the environment (low- quality E)

Factors Sustaining Life Cycling of Matter (Nutrients) There is a fixed supply of nutrients/matter Round trips must be done Time involved varies from seconds to centuries

Factors Sustaining Life Gravity Keeps the atmosphere around! Enables movement Enables cycling

THE FLOW OF ENERGY AND NUTRIENTS

What Happens to Solar Energy? Comes to earth as shortwave radiation UV and visible light 30% is reflected back into space (albedo) 20% is absorbed by the atmosphere 50% absorbed by the surface

What Happens to Solar Energy? Absorbed energy: Land, water heat up They re-radiate in longer wavelengths (IR) This IR is absorbed or “trapped” by CO 2, H 2 O, etc. Air heats up – Greenhouse effect <0.1% is used by green plants

Ecosystem Components Living and Nonliving Abiotic: the nonliving portion; water, air, nutrients, rocks, heat, solar energy Biotic: the living and once-living; plants, animals, microbes, dead organisms, and waste products Range of Tolerance: varies for each population in an ecosystem; optimum levels

Ecosystem Components Abiotic Factors Limiting Factors regulate population growth On land these include precipitation, temperature, nutrients; too much is just as bad as too little Aquatic: temperature, sunlight, nutrients

Ecosystem Components Producers and Consumers Trophic Level (feeding level): determined by food source of the organism; energy & nutrients are transferred through levels Autotrophs (Producers): make their own food – Land: plants; – Open water: phytoplankton – Most: photosynthesis; near hydrothermal vents - chemosynthesis

Ecosystem Components (Heterotrophs) Consumers: – Primary: Herbivores – Secondary (carnivores); ex – spiders, frogs, birds – Tertiary (third) or higher; feed on other carnivores – Other terms: omnivores, decomposers, detritivores

Ecosystem Components Aerobic Respiration: – Occurs in cells, energy is obtained from glucose and oxygen – Products are CO 2 and H 2 O Anaerobic Respiration (Fermentation) – Done by some decomposers – Breakdown of glucose w/out O 2 ; products are methane, ethanol, acetic acid, and H 2 S

Ecosystem Components Energy Flow and Nutrient Cycling The importance of decomposers There would be little, if any, nutrient cycling without detritus feeders

Energy Flow Energy Flows Through Trophic Levels Food Chain: sequence of organisms, each of which serves as a food or energy source for the next Food Web: network of interconnected food chains; most consumers feed on more than one type of organism

Energy Flow Usable Energy ↓ With Each Link Biomass: dry wt. of all the organic matter at a trophic level Energy transfer is not efficient Ecological Efficiency is the % of usable chemical energy in each trophic transfer – 10% is typical – Follows a pyramidal flow

Energy Flow Production Rates Gross Primary Productivity: rate at which an ecosystem’s producers convert solar E to chem E as biomass Measured in kcal/m 3 /yr Net Primary Productivity (NPP): rate of chem E production minus the rate at which E is used

The Flow of Matter Water Cycle: collects, purifies, & distributes H 2 O Evaporation Condensation (precipitation) Transpiration Surface runoff: feeds lakes, streams, etc. Stored: glaciers, aquifers, etc Humans alter in 3 ways: over-withdrawal, clearing vegetation (erosion), increase flooding ( by draining wetlands)

The Flow of Matter Carbon Cycle (Predominant form: CO 2 ) Producers remove CO 2 through photosynthesis Consumers and decomposers return it via respiration. Human alter in a big way: Fossil fuels are the result of millions of years of compression of organic material; storing CO 2. In the past 100 years, we have released all that CO 2

The Flow of Matter Nitrogen Cycle 78% of the air = N 2 ; cannot be fixed (exceptions) 2 natural fixers: lightning, bacteria Fixation: N 2 → NH 3 → NH 4 + (ammonium ion) Nitrification: NH 3, NH 4 + → NO 3 - (used by plants) Denitrification: NH 3 → N 2 (back into air)

The Flow of Matter Nitrogen Cycle: Human Impact NO production → acid rain N 2 O (livestock waste) → greenhouse gas Deforestation, etc. → release of N2 Ag runoff → ↑ NO 3 - Removal of N from topsoil during harvest

The Flow of Matter Phosphorus Cycle (does not use atmosphere) Major reservoir: PO 4 3- in rocks, ocean sediment Water erodes P from rock, picked up by plants Limiting factor in plant growth Human impact: making fertilizer, runoff

The Flow of Matter Sulfur Cycle Major underground reservoirs, ocean sediment Volcanic eruptions (H2S) Atmospheric SO x → acid rain Human impact: burning coal