Ecology

Unit 2

Chapter 3 – The Biosphere

Introduction to Introduction to EcologyEcology

Ecology - the scientific study of interactions among organisms and between organisms and their physical environment.

Ecologist - a scientist who studies organisms as they interact with other organisms within an ecosystem

Levels of OrganizationLevels of Organization Individual Organism Population—a group of individuals that belong to the

same species and live in the same area Community—an assemblage of different populations

that live together in a defined area Ecosystem—all the organisms that live in a place,

together with their physical environment Biome—a group of ecosystems that share similar

climates and typical organisms Biosphere—our entire planet, with all its organisms and

physical environments

Types of EcosystemsTypes of EcosystemsNatural

Ecosystems Self sustaining Precipitation Sunlight All resources to

support life Destroyed by

natural disasters (fires)

Human-Made Ecosystems

Not self sustaining Farms Cities Flower gardens Aquariums Zoo Huge inputs of

resources and energy

Relationships Within an EcosystemRelationships Within an Ecosystem•An ecosystem is a group of organisms that live together and interact with each other and their environment. •Organisms respond to their environments and can change their environments, producing an ever-changing biosphere.

Biotic Biotic FactorsFactors

Anything living in an ecosystem!List three

example of biotic components in an ecosystem and how they interact?

Abiotic Factors•Anything non-living!▫List three example of abiotic components in an ecosystem and why they are important?

BiomesBiomes• A large geographic region

determined by climate, soil type and plant life.

oWhy is plant life so important to an ecosystem?

BiomesBiomes

Arctic Tundra Northern Coniferous Forest or Taiga

Temperate Deciduous Forest

Temperate Grasslands or Prairie

Desert Tropical Savanna Tropical Rain Forest

Population StudiesPopulation Studies: factors that : factors that

affect the size of a populationaffect the size of a population

1. Carrying capacity:The maximum size of the population that an ecosystem can hold

2. Limiting factors: Anything that

prevents the population size

from increasingExamples ?

Food Chains and Food Food Chains and Food WebsWebs

o How does energy flow through ecosystems?

o Energy flows through an ecosystem in a one-way stream, from primaryo producers to various consumers. Energy moves from the “eaten” to the “eater.”

Where it goes from there depends on who eats whom!

Food ChainFood Chain

Leaf Grasshopper Frog Heron

The arrows in a food chain show what eats what. The arrow replaces the phrase “is eaten by”.

The arrow must point toward the “eater”.

Food WebsFood Webs•This is who eats who or what in the ecosystem. Each organism has a “job title” that describes their role. Anything that affects one level will probably affect the entire ecosystem!

Food WebFood Web

A food web shows the many possible food chains that exist in an ecosystem.

Food Webs “Job Food Webs “Job Titles”Titles”

• Producers- Plants. They are the basis for life in the ecosystem.

• These organisms are also called autotrophs.

Most Producers get Energy From the SunMost Producers get Energy From the SunThe best-known and most common primary producers harness solar energy through the process of photosynthesis.

Photosynthesis captures light energy and uses it to power chemical reactions that convert carbon dioxide and water into oxygen and energy-rich carbohydrates. This process adds oxygen to the atmosphere and removes carbon dioxide.

Most photosynthesis occurs in plants on land and algae in water ecosystems.

Life Without LightLife Without LightDeep-sea ecosystems depend on primary producers

that harness chemical energy from inorganic molecules such as hydrogen sulfide.

The use of chemical energy to produce carbohydrates is called chemosynthesis.

Food Webs “Job Food Webs “Job Titles”Titles”

•Consumers- these organism eat other organisms. They can not make their own food, therefore, they must “order out”!

•Organisms that must acquire energy from other organisms by ingesting in some way are also known as heterotrophs.

Food Webs “Job Food Webs “Job Titles”Titles”

•Consumers may be herbivores (plant eaters), carnivores (meat eaters) or omnivores (both)

•Carnivores are usually referred to as predators!

Food Webs “Job Food Webs “Job Titles”Titles”

▫1st or PRIMARY level consumers are herbivores

▫2nd or SECONDARY level consumers are carnivores or omnivores and eat 1st order consumers

▫What are 3rd order (level) consumers?

Food Webs “Job Food Webs “Job Titles”Titles”

•Decomposers- These are the recycling centers of the ecosystem. They break-down dead organisms into nutrients in the soil that plants can use as vitamins.▫Bacteria and Fungus

•Detritivores, feed on detritus particles (what is left from the decomposers,) often chewing or grinding them into smaller pieces.

giant earthworms

Food Webs “Job Food Webs “Job Titles”Titles”

Scavengers- Similar to decomposers because they eat already dead organisms and return nutrients to the soil.

Animals, birds, insects

Trophic Levels and Trophic Levels and Ecological PyramidsEcological Pyramids

o Each step in a food chain or food web is called a trophic level. • Primary producers always make up the first trophic level. • Various consumers occupy every other level. Some examples

are shown.o Ecological pyramids show the relative amount of energy or matter

contained within each trophic level in a given food chain or food web.

Advantages and Disadvantages Advantages and Disadvantages

of the Pyramidsof the Pyramids• Pyramids of numbers and biomass can

sometimes be inverted due to certain situations within ecosystems

• These inverted pyramids then lose their ability to accurately represent the passage of energy from one trophic level to the next

Pyramid Pyramid

of of

NumbersNumbers• This

represents the number of organisms that occupy each trophic level

http://openlearn.open.ac.uk

Pyramids of Energy Pyramids of Energy o Pyramids of energy show the relative amount of energy

available at each trophic level.o On average, about 10 percent of the energy available within

one trophic level is transferred to the next trophic level.o The more levels that exist between a producer and a

consumer, the smaller the percentage of the original energy from producers that is available to that consumer.

Pyramid of BiomassPyramid of Biomass

o The total amount of living tissue within a given trophic level is called its biomass.

o A pyramid of biomass illustrates the relative amount of living organic matter at each trophic level.

Recycling in the BiosphereRecycling in the Biosphereo Unlike the one-way flow of energy, matter is recycled

within and between ecosystems. o Elements pass from one organism to another and

among parts of the biosphere through closed loops called biogeochemical cycles, which are powered by the flow of energy.

• Biogeochemical cycles of matter involve biological processes, geological processes, and chemical processes.

Recycling in the BiosphereRecycling in the Biosphereo As matter moves through these cycles, it is

never created or destroyed—just changed.

• Biogeochemical cycles of matter pass the same atoms and molecules around again and again.

Water CycleWater Cycle• Also called the Hydrologic

Cycle• Movement and storage of

water on the planeto Total amount of water

doesn’t change – it is transported around the earth

o Energy to run the cycle comes from the sun

• Water re-enters that atmosphere by two processes

o Evaporation changes surface water (lakes, rivers, oceans) to water vapor• Water vapor (gaseous state) returns

to the atmosphereo Transpiration is the loss of water vapor

from the leaves of plants• Stomata are openings in leaves which

allow the water vapor out of the plant

• Condensationo As the water vapor rises in the atmosphere, it

looses energy (cools down)o Water droplets are formed from the water

vapor• Precipitation

o When the water droplets get too heavy it falls from the sky

o Weather conditions determine the type of precipitation – rain, snow, sleet

• Some precipitation re-evaporates before it reaches the ground

• Most precipitation falls into existing bodies of watero 70% of the earth’s surface is water

• The rest falls on lando Absorbed into the soil or flows over the surface

as Runoff (back to the oceans/lakes) o Infiltration is the process of water entering the

ground

The cycle begins again: o Evaporation and transpirationo Condensationo Precipitationo Runoff and Infiltration

The amount of precipitation is an important factor in the type of ecosystem and the population of organisms it can support

Nutrient CyclesNutrient Cycleso The chemical substances that an organism

needs to sustain life are called nutrients.

o Every organism needs nutrients to build tissues and carry out life functions.

o Nutrients pass through organisms and the environment through biogeochemical cycles.

The Carbon – Oxygen The Carbon – Oxygen Cycle Cycle

o Carbon is a major component of all organic compounds, including carbohydrates, lipids, proteins, and nucleic acids.

The Carbon – Oxygen The Carbon – Oxygen Cycle Cycle

• Plants take in carbon dioxide during photosynthesis and use the carbon to build carbohydrates.

• Carbohydrates then pass through food webs to consumers.

• Organisms release carbon in the form of carbon dioxide gas by respiration.

The Nitrogen Cycle The Nitrogen Cycle o All organisms require nitrogen to make amino acids,

which are used to build proteins and nucleic acids, which combine to form DNA and RNA.

The Nitrogen Cycle The Nitrogen Cycle

o Nitrogen-containing substances such as ammonia (NH3), nitrate ions (NO3), and nitrite ions (NO2) are found in soil, in the wastes produced by many organisms, and in dead and decaying organic matter.

The Nitrogen Cycle The Nitrogen Cycle o Nitrogen gas (N2) makes up 78 percent of Earth’s

atmosphere.• Although nitrogen gas is the most abundant form

of nitrogen on Earth, only certain types of bacteria that live in the soil and on the roots of legumes can use this form directly.

o The bacteria convert nitrogen gas into ammonia, in a process known as nitrogen fixation.

The Nitrogen Cycle The Nitrogen Cycle o Other soil bacteria convert fixed nitrogen into nitrates

and nitrites that primary producers can use to make proteins and nucleic acids.

o Consumers eat the producers and reuse nitrogen to make their own nitrogen-containing compounds

The Nitrogen Cycle The Nitrogen Cycle o Consumers eat the producers and reuse nitrogen to

make their own nitrogen-containing compounds. o Decomposers release nitrogen from waste and dead

organisms as ammonia, nitrates, and nitrites that producers may take up again.

The Nitrogen Cycle The Nitrogen Cycle o Other soil bacteria obtain energy by converting

nitrates into nitrogen gas, which is released into the atmosphere in a process called denitrification.

o A small amount of nitrogen gas is converted to usable forms by lightning in a process called atmospheric nitrogen fixation.

o Humans add nitrogen to the biosphere through the manufacture and use of fertilizers. Excess fertilizer is often carried into surface water or groundwater by precipitation.

The Phosphorus Cycle The Phosphorus Cycle o Phosphorus forms a part of vital molecules such as

DNA and RNA. o Although phosphorus is of great biological

importance, it is not abundant in the biosphere. o Phosphorus in the form of inorganic phosphate

remains mostly on land, in the form of phosphate rock and soil minerals, and in the ocean, as dissolved phosphate and phosphate sediments.

The Phosphorus Cycle The Phosphorus Cycle o As rocks and sediments wear down, phosphate is

releasedo Plants bind phosphate into organic compounds when

they absorb it from soil or water. o Organic phosphate moves through the food web, from

producers to consumers, and to the rest of the ecosystem.

Nutrient LimitationNutrient Limitationo Ecologists are often interested in an ecosystem’s

primary productivity—the rate at which primary producers create organic material.

o A nutrient whose supply limits productivity is called the limiting nutrient.

▫All nutrient cycles work together like the gears shown.

▫If any nutrient is in short supply—if any wheel “sticks”—the whole system slows down or stops altogether.

Nutrient Limitation in Aquatic Nutrient Limitation in Aquatic

Ecosystems Ecosystems o Sometimes an aquatic ecosystem receives a large

input of a limiting nutrient—for example, runoff from heavily fertilized fields.

o The result of this runoff can be an algal bloom—a dramatic increase in the amount of algae and other primary producers due to the increase in nutrients.

Energy flow in Energy flow in ecosystemsecosystems

What is an ecosystem?What is an ecosystem?• System = regularly interacting and

interdependent components forming a unified whole

• Ecosystem = an ecological system;•

= a community and its physical environment treated together as a functional system

OR, MORE SIMPLYOR, MORE SIMPLY• an ecosystem is composed of the

organisms and physical environment of a specified area.

• SIZE: micro to MACRO

Attributes of EcosystemsAttributes of Ecosystems• Order• Development• Metabolism (energy flow) 10% RULE• Material cycles• Response to the environment• Porous boundaries

• Emphasis on function, not species

ENERGY FLOW IN ECOSYSTEMSENERGY FLOW IN ECOSYSTEMS• All organisms require energy,

for growth, maintenance, reproduction, locomotion, etc.

• Hence, for all organisms there must be:A source of energy

•A loss of usable energy

Types of energyTypes of energy

• heat energy

• mechanical energy (+gravitational energy, etc.)

• chemical energy = energy stored in • molecular bonds

Transformations of Transformations of energyenergy

• How is solar energy converted to chemical energy?

An ecosystem has An ecosystem has abiotic and biotic abiotic and biotic

components:components:• ABIOTIC components:

• Solar energy provides practically all the energy for ecosystems.

• Inorganic substances, e.g., sulfur, boron, tend to cycle through ecosystems.

• Organic compounds, such as proteins, carbohydrates, lipids, and other complex molecules, form a link between biotic and abiotic components of the system.

BIOTIC BIOTIC componentcomponent

s:s:• The biotic components of an ecosystem

can be classified according to their mode of energy acquisition.

• In this type of classification, there are:

• Autotrophs• and • Heterotrophs

AutotrophsAutotrophs• Autotrophs (=self-nourishing) are called primary producers.

• Photoautotrophs fix energy from the sun and store it in complex organic compounds

• (= green plants, algae, some bacteria)

photoautotrophssimpleinorganiccompounds

complexorganic compounds

light

• Chemoautotrophs (chemosynthesizers) are bacteria that oxidize reduced inorganic substances

• (typically sulfur and ammonia compounds) • and produce complex organic

compounds.

chemoautotrophsreducedinorganiccompounds

complexorganic compounds

oxygen

Chemosynthesis near hydrothermal Chemosynthesis near hydrothermal

ventsvents

Other chemoautotrophs:

Nitrifying bacteria in the soil under our feet!

HeterotrophsHeterotrophs• Heterotrophs (=other-nourishing) cannot produce their own food directly from sunlight+ inorganic compounds. They require energy previously stored in complex molecules.

heterotrophssimpleinorganiccompounds

complexorganic compounds

(this may include several steps, with

several different types of organisms)

heat

• Heterotrophs can be grouped as:•

• consumers

• decomposers

• Consumers feed on organisms or particulate organic matter.

• Decomposers utilize complex compounds in dead protoplasm.

• Bacteria and fungi are the main groups of decomposers.

• Bacteria are the main feeders on animal material.

• Fungi feed primarily on plants, although bacteria also are important in some plant decomposition processes.

Energy flowEnergy flow• Simplistically:

• This pattern of energy flow among different organisms is the TROPHIC STRUCTURE of an ecosystem.

heat

Producers Consumers

Decomposers

heat

• It is useful to distinguish different types of organisms within these major groups, particularly within the consumer group.

Consumers

Terminology of Terminology of trophic levelstrophic levels

• We can further separate the TROPHIC LEVELS, particularly the Consumers:

• Producers (Plants, algae, cyanobacteria; some chemotrophs)--capture energy, produce complex organic compounds

• Primary consumers--feed on producers

• Secondary consumers--feed on primary consumers

• Tertiary consumers--feed on secondary consumers

More trophic levels:More trophic levels:• Detritivores--invertebrates that feed

on organic wastes and dead organisms (detritus) from all trophic levels

• Decomposers--bacteria and fungi that break down dead material into inorganic materials

Alternate TerminologyAlternate Terminology• Producers = plants etc. that capture energy from the sun

• Herbivores = plant-eaters• Carnivores = animal-eaters

• Omnivores--eat both animals and plants

• Specialized herbivores:• Granivores--seed-eaters• Frugivores--fruit-eaters

• Together, these groups make up a FOOD CHAIN

• E.g., grass, rabbit, eagle

Carnivore

Herbivore

Producer

CarnivoresCarnivores• Carnivores can be further

divided into groups:

• quaternary carnivore (top)• tertiary carnivore• secondary carnivore• primary carnivore

• The last carnivore in a chain, which is not usually eaten by any other carnivore, is often referred to as the top carnivore.

FoodFoodchainschains

ProblemsProblems

• Too simplistic• • No detritivores

• Chains too long

• Rarely are things as simple as grass, rabbit, hawk, or indeed any simple linear sequence of organisms.

• More typically, there are multiple interactions, so that we end up with a FOOD WEB.

Energy transfers Energy transfers among trophic levelsamong trophic levels

• How much energy is passed from one trophic level to the next?

• How efficient are such transfers?

• Biomass--the dry mass of organic material in the organism(s).

• (the mass of water is not usually included, since water content is variable and contains no usable energy)

• Standing crop--the amount of biomass present at any point in time.

Primary productivityPrimary productivity• Primary productivity is the rate of energy capture

by producers.• = the amount of new biomass of producers, per

unit time and space

Ecological pyramidsEcological pyramids• The standing crop, productivity, number of

organisms, etc. of an ecosystem can be conveniently depicted using “pyramids”, where the size of each compartment represents the amount of the item in each trophic level of a food chain.

• Note that the complexities of the interactions in a food web are not shown in a pyramid; but, pyramids are often useful conceptual devices--they give one a sense of the overall form of the trophic structure of an ecosystem.

producersherbivorescarnivores

Pyramid of energyPyramid of energy• A pyramid of energy depicts the energy

flow, or productivity, of each trophic level.

• Due to the Laws of Thermodynamics, each higher level must be smaller than lower levels, due to loss of some energy as heat (via respiration) within each level.

producersherbivorescarnivores

Energy flow in :

Pyramid of numbersPyramid of numbers• A pyramid of numbers indicates the number of individuals in each trophic level.

• • Since the size of individuals may vary widely

and may not indicate the productivity of that individual, pyramids of numbers say little or nothing about the amount of energy moving through the ecosystem.

# of producers# of herbivores# of carnivores

Pyramid of standing Pyramid of standing cropcrop

• A pyramid of standing crop indicates how much biomass is present in each trophic level at any one time.

• As for pyramids of numbers, a pyramid of standing crop may not well reflect the flow of energy through the system, due to different sizes and growth rates of organisms.

biomass of producersbiomass of herbivoresbiomass of carnivores

(at one point in time)

Inverted pyramidsInverted pyramids• A pyramid of standing crop (or of

numbers) may be inverted, i.e., a higher trophic level may have a larger standing crop than a lower trophic level.

• This can occur if the lower trophic level has a high rate of turnover of small individuals (and high rate of productivity), such that the First and Second Laws of Thermodynamics are not violated.

biomass of producersbiomass of herbivoresbiomass of carnivores

(at one point in time)

Pyramid of yearly Pyramid of yearly biomass productionbiomass production

• If the biomass produced by a trophic level is summed over a year (or the appropriate complete cycle period), then the pyramid of total biomass produced must resemble the pyramid of energy flow, since biomass can be equated to energy.

producersherbivorescarnivores

Yearly biomass production(or energy flow) of:

• Note that pyramids of energy and yearly biomass production can never be inverted, since this would violate the laws of thermodynamics.

• Pyramids of standing crop and numbers can be inverted, since the amount of organisms at any one time does not indicate the amount of energy flowing through the system.

• E.g., consider the amount of food you eat in a year compared to the amount on hand in your pantry.

Population – group of individuals of the same speciesliving in the same area, potentially interacting

Community – group of populations of different speciesliving in the same area, potentially interacting

What are some ecological interactions?

Ecological Interactions and Interdependence

Why are ecological interactions important?

Interactions can affect distribution and abundance.

Interactions can influence evolution.

Think about how the following interactions can affectdistribution, abundance, and evolution.

Types of ecological interactions & interdependence

competitionpredationparasitismmutualismcommensalismsymbiosis

Competition – two species share a requirement for alimited resource reduces fitness of one or both species

Predation – one species feeds on another enhancesfitness of predator but reduces fitness of prey

herbivory is a form ofpredation

Parasitism – one species feeds on another enhancesfitness of parasite but reduces fitness of host

Mutualism – two species provide resources or servicesto each other enhances fitness of both species

Commensalism – one species receives a benefit fromanother species enhances fitness of one species; noeffect on fitness of the other species

Symbiosis – two species live together can includeparasitism, mutualism, and commensalism

Organizing ecological interactions & interdependence

effect on species 1

effect onspecies 2

+ 0 -

+

0

-

mutualism

predationherbivoryparasitism

predationherbivoryparasitism

commensalism

commensalism

competition

competition

competition