Ecology

Chapter 18 Intro to Ecology

Ecology• Study of interactions between

organisms and the living and nonliving components of their environment

• All organisms interact with part of their environment

• Their survival depends on this Interdependence

Factors• Environmental factors separated into

2 categories1. Biotic factors: living components2. Abiotic factors: nonliving

components

BIOTIC or ABIOTIC?

Levels of organization• Environments and interactions can be

studied at many levelsOrganism- one member of a speciesPopulation- many members of the same species in the same are

Community- populations of different species living in the same area

Ecosytem- communities+ nonliving components

Biosphere- thin volume of Earth and atmosphere that support life (skin on an apple)

NICHE• Species do not occupy all

parts of their environment• Niche: specific role, or way of

life, of a species in its environment• Includes range of tolerances and Resources used

Generalists: broad niche (opossums)

Specialists: narrow niches (koalas)

ENERGY TRANSFER• Autotrophs make their own

food• They must capture energy

& use it to make organic molecules• They are producers

Most PHOTOSYNTHETICSome CHEMOSYNTHETIC:

energy stored in inorganic molecules to produce carbs

PRODUCTIVITY• GROSS PRIMARY PRODUCTIVITY:

rate at which producers capture light energy by making organic molecules

• Some organic molecules used for respiration• BIOMASS: organic material produced • NET PRIMARY PRODUCTIVITY:

rate at which biomass accumulates

CONSUMERS• Heterotrophs depend upon

autotrophs • CONSUMERS: Energy obtained

by eating organic molecules from other organisms•HERBIVORES: eat producers•CARNIVORES: eat other consumers•OMNIVORES: eat producers & consumers

DETRIVORES• Consumers that feed on

‘garbage’ (known as detritus)

• Detritus: waste, recently dead organisms, fallen leaves, etc.

• Decomposers: cause decay by breaking down complex molecules into simpler ones

ENERGY FLOW• When one organism eats another,

molecules are metabolized, & energy is transferred

• ENERGY flows from producers consumers

• Trophic levels: indicate an organism’s position in energy transfer sequence

FOOD WEBS AND CHAINS• Food chains: simple, linear feeding

relationships• Food webs: many interrelated food chains

ENERGY TRANSFER• Energy is lost as it moves through

ecosystems• heat

• ~10% of energy is available to next trophic level

• b/c energy transfers are limited, there are not many trophic levels in an ecosystem

• Also, # of individuals decreases at each trophic level

• Higher trophic levels contain less energy, so they support less individuals

Crash course: Ecology• https://www.youtube.com/watch?v=izRvPaAWgyw

Consider This…• Amount of U.S. grain fed to farm animals: 70%

• Pounds of corn and soy required to produce just one pound of pork: nearly 7

• Water needed to produce a pound of wheat: 14 gallons

• Water needed to produce a pound of meat: 441 gallons

• Of all water used for all purposes in the United States, more than half goes to: livestock production

Crash course: Water & Carbon cycles• https://www.youtube.com/watch?v=2D7hZpIYlCA

Water cycle

• Transpiration: water loss by plants through leaves• Evaporation: liquid water vapor

• EVAPOTRANSPIRATION = evaporation + transpiration

• Condensation: water vapor liquid

Crash Course: Nitrogen & Phosphorus Cycles• https://www.youtube.com/watch?v=leHy-Y_8nRs

Carbon cycle

photosynthesis

CO2

combustion

Respiration

Death and decay

Nitrogen cycle• Nitrogen in atmosphere is unusable (N2)• Plants can use nitrate (NO3)• Nitrogen fixation:

conversion of nitrogen gas into nitrateDone by nitrogen-fixing bacteria

• Bacteria live in roots of plantsPlants supply carbs, bacteria supply nitrogen

• Ammonification: formation of ammonia in soil by action of bacteria on decaying matter

• Nitrification: nitrites and nitrates produced by bacteria in soil

• Denitrification: returning of nitrogen to atmosphere

Phosphorous cycle• Plants get it from soil• Animals get it from plants• Phosphorous stored in mineral deposits• No atmospheric component

Ch 19 Populations

Crash Course: Populations• https://www.youtube.com/watch?v=RBOsqmBQBQ

k

Population characteristics• Population size•# of individuals

• Population density•# of individuals per unit area

• Dispersion • Clumped: individuals clustered together• Uniform: individuals separated by consistent distance• Random: each location independent of others

Population growth• Growth rate: amount by which a population

changes over a given time• Affected by 4 factors:

1. Immigration2. Emigration3. Birth rate4. Death rate

2 Types of Growth Curves1. Exponential Growth• Ideal Conditions• No Limiting Factors• Constant Growth Rate• “J” Shaped Curve

2. Logistic Growth• Limiting Factors Present• Falling Growth rate• “S” Shaped Curve• Resources become less available

Exponential Growth

Exponential Growth

Let’s examine bacteria…If a species of bacteria can reproduce once

every 20 minutes. • How many bacteria will there be after one

day?• How is this unrealistic?

Growth Curves Continued• Under ideal conditions•Growth continues

• However there are limiting factors•1. nutrients•2. space•3. competition

Logistic Growth

Logistic Growth

• Population growth slows or stops•Resources become less available

Carrying Capacity• Largest number of individuals (species)

that a given environment can supportNu

mbe

r of Y

east

Cel

ls

Time (hours)

Carrying capacity

Limiting Factors• Any factor that causes population

growth to decrease

Example:•Competition•Predation•Parasitism and disease•Drought and climate extremes•Human disturbances

Density-Dependent factors• Limiting factor that depends on

population size.

Example•Competition•Predation•Parasitism•Disease

Density-Independent Factors• Affects all populations in similar ways• Regardless of population size

Examples• Unusual weather• Natural disasters• Seasonal cycles• Human activities (damming rivers / clear-

cutting forests)

Resurrecting the Past (2:09 mins)

• http://www.cbsnews.com/videos/the-fast-draw-resurrecting-the-past/

Ch 20 Community Ecology

COMMUNITY ECOLOGY• Species interactions govern communities• Five main interactions1. Predation2. Competition3. Parasitism4. Mutualism5. Commensalism

Predation• When a predator eats an individual from another

species• Relationship between predator and prey

influences size of each population• Predator adaptations• Fangs• Venom• Speed• Specific teeth

Prey adaptations• Main strategy is avoidance• Speed or camoflauge• Batesian mimicry: harmless species mimics a

harful one• Mullerian mimicry: two or more harmful species

look similar

Competition • Occurs when niches overlap• Interspecific: competition between two or more

species• Intraspecific: between members of the same

species• One species usually gets pushed out or removed

from a community• Competitive exclusion

Symbiosis • Symbiosis: close, long-

term relationship between 2 organisms

• Parasitism: one individual is harmed; other benefits• Parasites live on or in a host

• Mutualism: both individuals benefit

• Commensalism: one benefits, other is unaffected

Species richness• Number of species in

a community• Varies with latitude• Greatest in tropical

rain forests because they are very stable

Successional changes• Ecological succession: gradual, sequential

growth or regrowth of a community• Follows disturbances• Primary succession: development of a

community where one has not previously existed• glacial retreat, volcanoes

• Secondary succession: sequential replacement of species following a disturbance• Fires, floods, • Climax community: stable end point following

succession