Unit 2, Chapter 4Unit 2, Chapter 4

Ecology, Ecosystems, and Food Webs

4-1 Ecology and Life4-1 Ecology and Life

Ecology- study of relationships between organisms and their environment Ecology examines how

organisms interact with their nonliving (abiotic) environment such as sunlight, temperature, moisture, and vital nutrients

Biotic interaction among organisms, populations, communities, ecosystems, and the ecosphere

Characteristics of LifeCharacteristics of Life

Organisms are composed of cells that have highly organized internal structure;Cells of organisms contain deoxyribonucleic acid (DNA), which form the basis of heredity;Organisms capture & transform matter & energy from their environment to supply needs for growth, survival, & reproduction;Organisms maintain favorable internal conditions, despite changes in their environment, through homeostasis;Organisms perpetuate themselves through reproduction;Organisms adapt to changes in environmental conditions through evolution.

OrganismsOrganismsorganism: any form of life.

organisms are classified into species.

species: groups of organisms that resemble each other, &, in cases of sexually reproducing organisms, can potentially interbreed.

estimates of 5 to 100 million species, most are insects & microorganisms; so far only about 1.8 million named; each species result of long evolutionary history.

wild species: population that exists in its natural habitat (= native species).

domesticated or introduced species: population introduced by humans (= non–native species).

Distinction between SpeciesDistinction between Species

Wild species- one that exists as a population of individuals in a natural habitat, ideally similar to the one in which its ancestors evolved

Domesticated species- animals such as cows, sheep, food crops, animals in zoos

VocabularyVocabulary

Population Group of interacting individuals of the same species

that occupy a specific area at the same time Genetic Diversity

Populations that are dynamic groups that change in size, age distribution, density, and genetic composition as a result of changes in environmental conditions

Habitat Place where a population or individual organism

naturally lives Community

Complex interacting network of plants, animals, and microorganisms

Ecosystem Community of different species interacting with

one another and with their nonliving environment of matter and energy

Ecosphere or Biosphere All earth's ecosystems

What is Life?What is Life?

All life shares a set of basic characteristics Made of cells that have highly

organized internal structure and functions

Characteristic types of deoxyribonucleic acid (DNA) molecules in each cell

Living OrganismsLiving Organisms

Capture and transform matter and energy from their environment to supply their needs for survival, growth, and reproduction

Maintain favorable internal conditions, despite changes in their external environment through homeostasis, if not overstressed

Living OrganismsLiving Organisms

Perpetuate themselves through reproduction Adapt to changes in environmental conditions

through the process of evolution

Biomes & Life Zonesbiome: large regions characterized by a distinct climate &

specific life–forms, especially vegetation, adapted to the region.major biomes: temperate grassland, temperate

deciduous forest, desert, tropical rain forest, tropical deciduous forest, tropical savannah, coniferous forest, tundra

aquatic life zone: major marine or freshwater areas containing numerous ecosystems.major aquatic life zones: lakes, streams, estuaries,

coastlines, coral reefs, & the deep ocean

BiomesBiomes – Large regions characterized by distinct climate, and specific life-forms

ClimateClimate – Long-term weather; main factor determining what type of life will be in a certain area.

www.sws.uiuc.edu/nitro/biggraph.asp

4-2 Geosphere4-2 Geosphere

Lithosphere Crust and upper mantle

Crust Outermost, thin silicate zone, eight

elements make up 98.5% of the weight of the earth’s crust

The Earth contains several layers or concentric spheres

4-2 Geosphere4-2 Geosphere Mantle

Surrounded by a thick, solid zone, largest zone, rich with iron, silicon, oxygen, and magnesium, very hot

Core Innermost zone, mostly iron, solid

inner part, surrounded by a liquid core of molten material

Inner Core is hotter than surface of the Sun

Thin envelope of air around the planet Troposphere

extends about 17 kilometers above sea level, contains nitrogen (78%), oxygen(21%), and is where weather occurs

Stratosphere 17-48 kilometers above sea

level, lower portions contains enough ozone (O3) to filter out most of the sun’s ultraviolet radiation

4-2 Atmosphere4-2 Atmosphere

Consists of the earth’s liquid water, ice, and

water vapor in the atmosphere

4-2 Hydrosphere4-2 Hydrosphere

What Sustains What Sustains Life on Earth?Life on Earth?

Life on the earth depends on three interconnected factors One-way flow of high-quality energy

from the sun Cycling of matter or nutrients (all

atoms, ions, or molecules needed for survival by living organisms), through all parts of the ecosphere

Gravity, which allows the planet to hold onto its atmosphere and causes the downward movement of chemicals in the matter cycles

SunSun

Fireball of hydrogen (72%) and helium (28%)

Nuclear fusion Sun has existed for 6 billion years Sun will stay for another 6.5 billion years Visible light that reaches troposphere is

the ultraviolet ray which is not absorbed in ozone

Solar EnergySolar Energy

72% of solar energy warms the lands 0.023% of solar energy is captured by green

plants and bacteria Powers the cycling of matter and weather

system Distributes heat and fresh water

www.bom.gov.au/lam/climate/levelthree/ climch/clichgr1.htm

Energy FlowEnergy FlowThe ultimate source of energy in most ecosystems is the sun.

Energy Flow & Nutrient CyclingEnergy Flow & Nutrient Cycling

Life on Earth depends upon one–way flow of high–quality energy from sun & cycling of crucial elements.

Type of Nutrientsnutrient: any atom, ion, or molecule an organism needs to live, grow, or reproduce.

macronutrients needed in relatively large amountse.g., C, O, H, N, P, S, K, Ca, Mg, Fe

micronutrients needed in relatively small amountse.g., Na, Zn, Cu, Cl, I

nutrient cycles (= biogeochemical cycles) involve continual flow of nutrients from nonliving (air, water, soil, rock) to living organisms (biota) & back again.

nutrient cycles driven directly or indirectly by solar radiation & gravity.

Major cycles: hydrologic (water), carbon, oxygen, nitrogen, phosphorus, & sulfur.

Closed System: a system in which energy, but not matter, is exchanged between the system & its environment.

– earth is a closed system, in that matter is neither lost nor gained (except negligible cosmic dust & meteorites) while energy flows through;

Open System: a system in which both energy & matter are exchanged between the system & its environment.

– organisms are open systems because both matter & energy are exchanged with the environment.

Open vs. Closed SystemsOpen vs. Closed Systems

Ecosphere SeparationEcosphere Separation

The Ecosphere and it’s ecosystem can be separated into two parts Abiotic- nonliving, components

Ex: air, water, solar energy Physical and chemical factors that influence living

organisms Biotic- living, components

Ex: plants and animals

Range of ToleranceRange of Tolerance

The survival, growth, & reproduction of organisms is determined, in part, by maximum & minimum tolerance limits for physical conditions such as temperature.

Fig. 4–12

Limiting FactorsLimiting Factors

limiting factor: an environmental factor that is more important than other factors in regulating survival, growth, or reproduction.

law of tolerance: the existence, abundance, & distribution of a species in an ecosystem is determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by that species.

limiting factor principle: too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance.

Dissolved Oxygen ContentDissolved Oxygen Content

Amount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure. Limiting factor of

aquatic ecosystem

SalinitySalinity

amount of salt dissolved in given volume of water

Major Living ComponentsMajor Living Components

Two main categories:

1) producers (also called autotrophs = "self–feeders") make their own food from compounds obtained in the environment.

most capture sunlight to make sugars & other organic compounds in a process called photosynthesis, e.g., green plants.

a few, mostly bacteria, convert simple compounds into complex nutrient compounds without sunlight, e.g., bacteria of thermal vents that use hydrogen sulfide (H2S) & carbon dioxide.

2) consumers (also called heterotrophs "other–feeders") get their energy & nutrients by feeding on other organisms or their remains.

Includes herbivores, carnivores, decomposers, etc.

Photosynthesis & RespirationPhotosynthesis & Respiration

photosynthesis: complex chemical reaction in plants, in which solar radiation is captured by chlorophyll (& other pigments) & used to combine carbon dioxide & water to produce carbohydrates (e.g., glucose), other organic compounds, & oxygen.

carbon dioxide + water + solar energy glucose + oxygen

6 CO2 + 6 H2O + solar energy C6H12O6+ O2

aerobic respiration: complex process that occurs in the cells of organisms, in which organic molecules (e.g., glucose) are combined with oxygen to produce carbon dioxide, water, & energy.

glucose + oxygen carbon dioxide + water + energy

C6H12O6+ O2 6 CO2 + 6 H2O + energy

Chemosynthesis-Chemosynthesis- Bacteria can convert simple

compounds from their environment into more complex nutrient compound without sunlight Ex: becomes consumed by

tubeworms, clams, crabs Bacteria can survive in great

amount of heat

ConsumersConsumers

major kinds of consumers (= heterotrophs)

primary consumers: (=herbivores) feed directly on producers;

secondary consumers: (=carnivores) feed on primary consumers;

tertiary consumers: feed only on carnivores;

omnivores: consumers that feed on both plants & animals;

scavengers: feed on dead organisms;

decomposers: consumers that complete the breakdown & recycling of organic materials from the remains & wastes of other organisms;

detritivores: feed on detritus (partially decomposed organic matter, such as leaf litter & animal dung).

Consumers or HeterotrophsConsumers or Heterotrophs

Obtain energy and nutrients by feeding on other organisms or their remains

ConsumersConsumers

Herbivores (plant-eaters) or primary consumers Feed directly on producers

Deer, goats, rabbits

http://www.holidays.net/easter/bunny1.htm

ConsumersConsumers

Carnivores (meat eater) or secondary consumers

Feed only on primary consumer Lion, Tiger

ConsumersConsumers

Tertiary (higher-level) consumer

Feed only on other carnivores Wolf

ConsumersConsumers

Omnivores- consumers that eat both plants and animals Ex: pigs, humans,

bears

ConsumersConsumers

Scavengers- feed on dead organisms Vultures, flies, crows, shark

Detritus Feeders vs. DecomposersDetritus Feeders vs. Decomposers

Fig. 4–13

ConsumersConsumers

Detritivores- live off detritus Detritus parts of dead

organisms and wastes of living organisms.

Detritus feeders- extract nutrients from partly decomposed organic matter plant debris, and animal dung.

ConsumersConsumers

Decomposers - Fungi and bacteria break down and recycle organic materials from organisms’ wastes and from dead organisms Food sources for worms

and insects Biodegradable - can be

broken down by decomposers

RespirationRespiration

Aerobic Respiration Uses oxygen to convert organic nutrients back into

carbon dioxide and water Glucose + oxygen Carbon dioxide + water +

energy Anaerobic Respiration or Fermentation

Breakdown of glucose in absence of oxygen

Summary of Ecosystem StructureSummary of Ecosystem Structure

Fig. 4–15

Food ChainFood Chain Food Chain-Series of organisms

in which each eats or decomposes the preceding one Decomposers complete the cycle

of matter by breaking down organic waste, dead animal. Plant litter and garbage.

Whether dead or alive organisms are potential (standard) sources of food for other organisms.

Second Law of EnergySecond Law of Energy

Organisms need high quality chemical energy to move, grow and reproduce, and this energy is converted into low-quality heat that flows into environment Trophic levels or feeding levels- Producer is a

first trophic level, primary consumer is second trophic level, secondary consumer is third.

Decomposers process detritus from all trophic levels.

Food Webs & Energy FlowFood Webs & Energy FlowFood chains involve a sequence of organisms, each of which is the food for the next.

Fig. 4–16

Food WebFood Web Complex network

of interconnected food chains

Food web and chains One-way flow of

energy Cycling of

nutrients through ecosystem

Food WebsFood Webs

Grazing Food Webs Energy and nutrients

move from plants to herbivores

Then through an array of carnivores

Eventually to decomposers

(100,000 Units of Energy)

Food WebsFood Webs

Grazing Food Webs Energy and nutrients

move from plants to herbivores

Then through an array of carnivores

Eventually to decomposers

(1,000 Units of Energy)

Food WebsFood Webs

Grazing Food Webs Energy and nutrients

move from plants to herbivores

Then through an array of carnivores

Eventually to decomposers

(100 Units of Energy)

Food WebsFood Webs

Grazing Food Webs Energy and nutrients

move from plants to herbivores

Then through an array of carnivores

Eventually to decomposers

(10 Units of Energy)

Food WebsFood Webs

Grazing Food Webs Energy and nutrients

move from plants to herbivores

Then through an array of carnivores

Eventually to decomposers

(1 Units of Energy)

Food WebsFood Webs

Detrital Food Webs Organic waste material

or detritus is the major food source

Energy flows mainly from producers (plants) to decomposers and detritivores.

Generalized Energy PyramidGeneralized Energy Pyramid

Fig. 4–19

In nature, ecological efficiency varies from 5% to 20% energy available between successive trophic levels (95% to 80% loss). About 10% efficiency is a general rule.

Pyramid of Energy FlowPyramid of Energy Flow Loss of usable energy as energy flows through

trophic levels of food chains and webs Rarely have more than 4 steps

Generalized Energy PyramidGeneralized Energy PyramidAnnual pyramid of energy flow (in kilocalories per square meter per year) for an aquatic ecosystem in Silver Springs, FL.

BiomassBiomass

Dry weight of all organic matter contained in organisms. Biomass is measured in dry weight

Water is not source of energy or nutrient Biomass of first trophic levels is dry mass of all

producers Useable energy transferred as biomass varies from

5%-20% (10% standard)

Biomass PyramidsBiomass Pyramids

Biomass pyramids, commonly measured as dry weight per square meter for each trophic level, can either mirror the energy pyramid (as for the abandoned field) or be inverted (as for the ocean). Inverted biomass pyramids result because the producers are eaten by consumers.

Pyramid of BiomassPyramid of BiomassStorage of biomass at various trophic levels of

ecosystem

Pyramid of NumbersPyramid of Numbers

Number of organisms at each trophic level

http://www.nicksnowden.net/Module_3_pages/ecosystems_energy_flows.htm

Pyramids of NumbersPyramids of Numbers

Fig. 4–22

Pyramids of numbers depend upon both the size of organisms (e.g., forests have smaller numbers of large producers than do grasslands) & the biomass pyramid.

Primary ProductivityPrimary Productivity

gross primary productivity (GPP) is the rate at which an ecosystem's producers convert solar energy into chemical energy as biomass.

net primary productivity (NPP) is the rate at which energy for use by consumers is stored in new biomass.

NPP = GPP – [rate at which producers use biomass]

Primary ProductivityPrimary Productivity

Estimated annual net primary productivity of major biomes & aquatic life zones, expressed as kilocalories per square meter per year.

Fig. 4–24

Primary ProductivityPrimary Productivity

Estimated annual contribution of the various types of biomes & aquatic life zones to Earth's overall net primary productivity. Note that the preceding figure gives the average net primary productivity per unit area.

Fig. 4–25

Gross Primary Productivity (GPP)Gross Primary Productivity (GPP)Rate in which

producers convert solar energy into chemical energy

(biomass) in a given amount

of time

Net Primary Productivity (NPP)Net Primary Productivity (NPP)

Rate in which energy for use by consumers is stored in new biomass of plants Measured in kilocalories per square meter per year

or grams in biomass NPP is the limit determining the planet’s carrying

capacity for all species. 59% of NPP occurs in land / 41% occurs in ocean

Ecological EfficiencyEcological Efficiency

Percentage of energy transferred from one trophic level to another. 10% ecological efficiency

1,000,000 units of energy from sun 10,000 units available for green plants (photosynthesis) 1000 units for herbivores 100 units for primary carnivores 10 units for secondary carnivores

Studying EcosystemsStudying Ecosystems

FIELD RESEARCH Going into nature and observing/measuring the structure of ecosystems Majority of what we know now comes from this type Disadvantage is that it is expensive, time-consuming, and difficult to carry out

experiments due to many variables LABORATORY RESEARCH

Set up, observation, and measurement of model ecosystems under laboratory conditions

Conditions can easily be controlled and are quick and cheap Disadvantage is that it is never certain whether or not result in a laboratory will

be the same as a result in a complex, natural ecosystem SYSTEMS ANALYSIS

Simulation of ecosystem rather than study real ecosystem Helps understand large and very complicated systems

Ecosystem ImportanceEcosystem Importance

Ecosystem services are the natural services or earth capital that support life on the earth

Essential to the quality of human life and to the functioning of the world’s economies

Ecosystem ImportanceEcosystem Importance

Ecosystem services include: Controlling and moderating climate Providing and renewing air, water, soil Recycling vital nutrients through chemical cycling Providing renewable and nonrenewable energy

sources and nonrenewable minerals Furnishing people with food, fiber, medicines,

timber, and paper

Ecosystem ImportanceEcosystem Importance

Ecosystem services include Pollinating crops and other plant species Absorbing, diluting, and detoxifying many

pollutants and toxic chemicals Helping control populations of pests and disease

organisms Slowing erosion and preventing flooding Providing biodiversity of genes and species

Why Is Biodiversity So Important? Why Is Biodiversity So Important?

Food, wood, fibers, energy, raw materials, industrial chemicals, medicines, …

Provides for billions of dollars in the global economy

Provides recycling, purification, and natural pest control

Represents the millions of years of adaptation, and is raw material for future adaptations

Two Principles of Ecosystem Two Principles of Ecosystem SustainabilitySustainability

Use renewable solar energy as energy source

Efficiently recycle nutrients organisms need for survival, growth, and reproduction