ECOLOGY UNIT

Chapter 2: Principles of EcologyChapter 3: Communities, Biomes and EcosystemsChapter 4: Population EcologyChapter 5: Biodiversity and Conservation

2.1 ORGANISMS AND THEIR RELATIONSHIPS

oEcology – scientific study of all the relationships that occur between organisms and their environment

oThe word ecology was first introduced in 1866 by a German biologist named Ernst Haeckel.

BIOTIC AND ABIOTIC FACTORS

oBiotic factors – living factors in an organism’s environment

oExamples - ?

oAbiotic factors – nonliving factors in an organism’s environment

oExamples – temperature, air currents, water currents, sunlight, soil, rainfall

LEVELS OF ORGANIZATION

Biosphere – portion of Earth that supports life Ecologists look at smaller portions of the biosphere

when studying ecological relationships interactive levels of org (look at p 37)

Biome

Ecosystem

Community

Population

Organism

ECOSYSTEM INTERACTIONS

Habitat – an area where an organism lives

Niche – role or position that an organism has in its environment.An organism’s niche describes how it meets its needs for food, shelter and reproduction

WHAT ORGANISMS ARE IN THIS HABITAT?

COMMUNITY INTERACTIONS

Competition – more than one organism uses a resource at the same timeResources are necessary for life and might

include food, water, space, light, and mates

Predation – the act of one organism consuming another

Mutualism – relationship between two or more organisms that live closely together and benefit from each other

Commensalism – relationship in which one organism benefits and the other organism is neither helped nor harmed

Parasitism – relationship in which one organism benefits at the expense of another organism

2.2 FLOW OF ENERGY Organisms differ in how they obtain

energy Everything that organisms do in

ecosystems requires energy. Where do organisms get their energy?

From the Sun (of course)!!

Autotroph – an organism that collects energy from sunlight to produce foodAutotrophs are also called producersAutotrophs capture energy from the Sun,

making it available for all members of an ecosystem

Heterotroph – an organism that gets its energy by consuming other organismsHeterotrophs are also called consumersHerbivores eat only plantsCarnivores prey on other heterotrophs for

foodOmnivores eat both plants and animalsDetritivores eat dead, decaying materialDecomposers break down dead material by

releasing digestive enzymes

MODELS OF ENERGY FLOW Ecologists use food chains and food

webs to model the energy flow through an ecosystem

Food chain – a single, straight-line path of energy that involves only 4-5 organisms

Food web - a bunch of food chains put together for a given habitat.

Each step in a food chain or food web is called a trophic level

Autotrophs make up the first trophic level

Heterotrophs make up the remaining levels

Food Chains

Vs.Food Webs

LOSS OF ENERGY IN A FOOD CHAIN

When an organism eats, almost half of the energy in the food is lost to the environment as heat.

The amount of useful energy available to do work decreases as energy passes through the ecosystem

Rule of 10Only 1/10 (10%) of energy is used by an

organism when it eatsThe other 90% is lost to the environment

ENERGY PYRAMIDS An energy pyramid is a diagram that

shows 3-4 trophic levels The size of each block is determined by

the amount of energy available

2.3 CYCLING MATERIALS There are 4 different cycles that

we find in the environmentWater, carbon, phosphorus, and nitrogen

A cycle is a pathway that describes how a chemical movesA substance enters a living

organismThe substance may stay in the

organism for some timeThat same substance eventually

leaves the organism and returns to the environment

THE WATER CYCLE IS VERY IMPORTANT TO LIVING THINGS!!

Freshwater constitutes only about 3% of all water on Earth

Water available for living organisms is about 31% of all freshwater

69 % of all freshwater is found in ice caps and glaciers

Even ocean-dwelling organisms rely on freshwater flowing to oceans to prevent high salt concentrations inside their body.

Steps:1. Evaporation from bodies of

water and/or transpiration from plants

2. Condensation in the form of clouds

3. Precipitation that falls as snow, rain, sleet, hail, etc.

4. Some precipitation is absorbed by the soil and stored as ground water.

Refer to page 46 interactive water cycle

THE CARBON CYCLE Carbon dioxide is absorbed by

plants to make their own food and produce oxygen

Carbon dioxide is released into the atmosphere in two ways:Respiration-breathingCombustion-burning of fossil fuels

What is a fossil fuel?List several types of fossil fuels

interactive carbon cycle

THE CARBON CYCLE

3.1 COMMUNITY ECOLOGY Community – a group of interacting

populations that occupy the same area at the same time

Limiting factor – any abiotic or biotic factor that restricts the numbers, reproduction or distribution of organisms in a communityExamples include: sunlight, climate,

water, temperature, nutrients, fire, soil, space

If the environment of the community changes, plants and animals have to:Adapt in order to surviveMigrate to a place that has resources

WHAT ORGANISMS WOULD YOU EXPECT TO FIND HERE?

SUCCESSION Ecosystems are constantly changing

A tree falls in the forestA forest fire wipes out a large community

Ecological succession – the change in an ecosystem that happens when one community replaces another as a result of changing abiotic and biotic factors

TWO TYPES OF SUCCESSION

Primary succession A change in the environment that allows an

area of land to support living things where it never did before

Examples: melting glaciers, volcano Secondary succession

A major (sometimes drastic) change in the environment that destroys much of what was living but allows for growth years later.

Examples: tornado, hurricane, forest fire, flood, windstorm

PRIMARY OR SECONDARY SUCCESSION?

PRIMARY OR SECONDARY SUCCESSION?

3.2 TERRESTRIAL BIOMES Weather – condition of the atmosphere

at a specific place and time. Important elements of weather:

Temperature Most organisms live best within a certain range

of temperatures There are three major climate zones: tropical,

temperate and arcticMoisture

All organisms require water, so they must find a place to live that satisfies their needs.

Elevation and ocean currentsVisualizing Global Effects on Climate (p 67)

BE FAMILIAR WITH… Major land biomes pp 68-72 Mountains p 72 Polar regions p 73 Freshwater ecosystems pp 74-77

Wetlands p 78 Estuaries p 78 Marine ecosystems p 79-81

4.1 POPULATION DYNAMICS

All species occur in groups called populations

Populations are characterized by:Population density – the number of

organisms in a given areaSpatial distribution – the pattern of

spacing of a population Three types: uniform, clumped, random Visualizing Population Characteristics (p 93)

Population ranges

FACTORS THAT LIMIT POPULATIONS

Density-independent factors – any factor in the environment that does not depend on the number of members in a populationExamples: drought, flooding, extreme heat

or cold, tornadoes, hurricanes Density-dependent factors – any factor

in the environment that depends on the number of members in the populationExamples: predation, disease, parasites,

and competition (see next slide)

POPULATION GROWTH RATE

PGR – how fast a given population growsDependent on birth rate and death rate

If a population has more births then deaths, the population is ______________

If a population experiences more deaths then births, the population is ____________

If a population has an equal number of births to deaths, the population is _____________

Also dependent on emigration and immigration Emigration – describes the number of people

moving away from a population Immigration – describes the number of people

moving into a population

POPULATION GROWTH CURVES

Exponential growth curve (j-curve)Occurs when the growth rate is proportional

to the size of the populationAll populations grow exponentially until

some limiting factor slows the population’s growth.

Logistic growth curve (s-curve)Occurs when the population’s growth slows

or stops following exponential growth when the population reaches it’s carrying capacity.

Carrying capacity – the maximum number of individuals in a species that an environment can support for the long term.

GROWTH CURVES

Exponential Growth

(J-curve)

Logistic Growth

(S-curve)

Boom & Bust

Population Crash

Oscillation Below

Carrying Capacity

4.2 HUMAN POPULATION Demography – the study of human

population size, density, distribution, movement, birth rate and death rate.1804 – estimated 1 billion people1999 – 6 billion people2011 – 7 billion people2020 – projected to be 8 billion

people

This looks like a J-curve, right? At what point to we reach carrying capacity?

WHY ARE PEOPLE LIVING LONGER?

Agriculture has improved, allowing more people to be fed by large crops (corn, soybeans, wheat, etc).

The breeding of animals (cows, pigs, chickens, etc) has increased food supplies.

Technology has given people more information at their fingertips.

Medications and vaccines have increased a person’s chance for survival by reducing the number of deaths from parasites and disease.

Improvements in shelter have helped people survive major weather disasters.

POPULATION PYRAMIDS Population pyramids show the age

structure of a given population. The age structure is the number of

males and females in each of three categories:Pre-reproductive:

ages 0-19Reproductive:

ages 20-44Post-reproductive:

ages 45-80+population pyramidanimation

HUMAN CARRYING CAPACITY

Many scientists suggest that human population growth needs to be reduced.

In many countries, voluntary population control is occurring.

In other countries, “mandatory” population control is occurring.

If human population continues to grow:areas become overcrowded and disease

and starvation will occurnatural resources become scarce (p 105)

5.1 BIODIVERSITY Biodiversity is the variety of life in an

area that is determined by the number of different species in that area.

The importance of biodiversityEconomic value

Humans depend on plants and animals for food, clothing, energy, and shelter

Medical/scientific value Medicines are derived from plants and animals The Madagascar periwinkle produces and extract

that has been used with leukemia patients to increase survival (p 119)

Aesthetic value Plants and animals give us a better appreciation

5.2 THREATS TO BIODIVERSITY

Scientists believe we are witnessing a period of mass extinction—an event in which a large percentage of all living species become extinct in a short period of time.

The current high rate of extinction is due to the activities of one species – HUMANS.

Humans are changing conditions on Earth so fast that it doesn’t allow other organisms to adapt and survive.

OVEREXPLOITATION Taking more individuals from a population than

the species can replace.Bison were hunted to near extinction for their meat

and furPassenger pigeons went extinct in the early 1900s

due to overhunting and urbanizationThe ocelot is hunted for the high value of its furRhinos are in danger of becoming extinct because

of poachers who kill them for the horns on their head

HABITAT LOSS Humans are clearing areas of land for housing

and are replacing native plants with food crops. The tropical rainforests contain much of the

world’s biodiversity. Removal of the forest will cause many species to become extinct.

Natural disasterscan cause disruption of habitats which in turn destroy food webs.

POLLUTION Pollution changes the composition of air, soil,

and water for all animals. There are lots of toxic substances put into the

air or dumped into the water or soil. Many of these substances accumulate in the tissues of living organisms.

Biological magnification describes the increasing concentration of toxic substances in organisms as trophic levels increase in food webs.

More and more news articles talk about mercury levels in fish. The more mercury in the water, the more mercury in fish tissue, the more mercury we consume when we eat fish.

INTRODUCED SPECIES Nonnative species that are either intentionally

or unintentionally transported to a new habitat are a threat to native species living in that area.

Lamprey of the Great Lakes Asian long-horned beetle Emerald ash borer

Acid Precipitation

More heavily populated areas have heavier amounts of acid rain.

Aquatic animals and plants slowly die from acidic levels in the water, forests are burned, animals are forced from their homes.

When fossil fuels are burned, compounds called sulfur dioxide and nitrogen oxide are released into the atmosphere. These compounds react with water and form acids that fall back to Earth in the form of precipitation.

EUTROPHICATION Occurs when fertilizers,

animal waste, and sewage rich in nitrogen and phosphorus flow into waterways, causing algae growth.

The algae use all the oxygen in the water and

suffocate plants and other aquatic species.

PROTECTING THE OZONE LAYER

Ozone is a compound made up of 3 oxygen molecules

The ozone layer is important because it protects living things from ultraviolet (UV) radiation

The ozone concentration is much lower over Antarctica

What destroys ozone? CFCs = cloroflourocarbons

found in coolants of old refrigerators and air conditioners

also found in aerosol chemicals of spray cans VOCs = volatile organic compounds

found in paints and varnishes, glue, caulk, air fresheners, cleaning and disinfecting products

CONTROLLING GREENHOUSE GASES

Human activity causes gases to be released into the atmosphere. These gases trap solar energy and help to insulate the Earth just like a greenhouse traps heat from the Sun.

Greenhouse gases include:Water vapor, carbon dioxide, and methane

Because humans still burn fossil fuels, carbon dioxide levels get higher and higher.

When water vapor and carbon dioxide are mixed in the atmosphere they trap the solar energy and contribute to the Earth’s rising temperature.

All of this trapped heat energy causes changes to weather patterns, making storms more severe across the globe.

Some of this trapped heat also causes the ice to melt (glaciers, ice sheets) at the north and south poles.

PROTECTING FRESH WATER Freshwater is in short supply because humans

pollute this very important resource How can you conserve water in your home?

The total usable freshwater supply for ecosystems and humans is less than 1 percent of all freshwater resources.

By 2025, 1.8 million people will be living in countries or regions with absolute water scarcity, and two-thirds of the world population could be under stress conditions.

The UN suggests that each person needs 20-50 liters of safe freshwater a day to ensure their basic needs for drinking, cooking and cleaning.

More than one in six people worldwide - 894 million - don't have access to this amount of safe freshwater.

Globally, diarrhea is the leading cause of illness and death, and 88 percent of diarrheal deaths are due to a lack of access to sanitation facilities.

Today 2.5 billion people, including almost one billion children, live without even basic sanitation.

Every 20 seconds, a child dies as a result of poor sanitation. That's 1.5 million preventable deaths each year.

The daily drinking water requirement per person is 2-4 liters, but it takes 2000 to 4000 liters of water to produce one person's daily food.

In 2007, the estimated number of undernourished people worldwide was 923 million.

By 2050, the world's water will have to support the agricultural systems that will feed an additional 2.7 billion people.

Every day, 2 million tons of human waste are disposed of in waterways.

In developing countries, 70 percent of industrial wastes are dumped untreated into waters where they pollute the usable water supply.

5.3 CONSERVING BIODIVERSITY As population increases, the need for

natural resources also increases, but usually at the expense of harming other species.Visualizing biodiversity hot spots

Nonrenewable resources are found in limited amounts and must be used carefully.Fossil fuels, minerals, water

Renewable resources have an endless supplySolar, wind

More people need to live sustainablyReduce the amount of resources consumedRecycle resources that can be recycledTake resources from an ecosystem

responsibly