Introduction to Ecology

Unit 1 Dynamics of Ecosystems

Picture This!

The plaintive call of the loon can be heard over a chorus of bullfrogs and red-wing blackbirds. Jewel-like dragonflies chase mosquitoes along the water’s edge. An eagle circles. A snapping turtle suns itself. Minnows dart in an out of wild rice in the shallows, while pike search for a meal in the deep. Two canoeists remark it is going to be a wonderful day.

All the living and non-living things described in the last scene are involved in delicately balanced interactions with one another. How do wild rice, snapping turtles, mosquitoes, and the water interact?

Vocabulary

The branch of biology that deals with the study of the interactions among organisms and with their environment is known as ecology.

The word “eco” comes from the Greek word oikos, which means house.

Scientists who study ecology are called ecologists.

Because our planet is so diverse, ecologists tend to study smaller areas called ecosystems.

There are 2 types of ecosystems

Terrestrial Ecosystem

An ecosystem contained on land

Located on continents and islands, water is a limiting factor

Aquatic or Marine Ecosystem

An ecosystem contained in water

Freshwater i.e. lakes

Salt Water/Marine i.e. oceans, lagoons

Ecosystems

An ecosystem consists of the physical environment (abiotic factors), and all the living things (biotic factors).

Abiotic Factors:

i.e. water, sunlight, oxygen, soil, nutrients, and temperature

Biotic Factors:

i.e. plants, animals, fungi, and bacteria that live with it.

Habitat vs. Niche

Each type of living thing in an ecosystem has a place in which it lives. This is known as a habitat.

The combination of the job an organism does and the place in which it lives is called a niche.

Examples of Jobs that Organisms Do

plants and algae trap the energy in sunlight

and produce their own food (and are hence

called producers)

animals are called consumers since they

cannot make their own food, and must obtain

the food from producers.

Bacteria and fungi are decomposers. They

eat dead plant and animal remains and convert

them into substances that can be reused.

Energy Flow

Food Chains

All living things require energy to live. The ultimate source of that energy is the sun. Producers such as plants and algae capture the sun’s energy and transform it into organic compounds (compounds that contain carbon). These compounds are used to build plant parts such as leaves and flowers, or store extra energy in roots and seeds.

Trophic levels – how many are there?

(trophic level refers to each stp in a food chain)

Tertiary consumers

Secondary consumers

Primary Consumers

Producers

Consumers can’t directly transform

sunlight into organic compounds…

Primary Consumers also known as herbivores, feed directly on plants. i.e. moose, cattle, grasshoppers, rabbits,

aphids

Secondary Consumers feed on primary consumers.

Tertiary Consumers feed on secondary consumers. The higher level (secondary and tertiary)

consumers are also known as carnivores. i.e. wolves, northern pike, eagles, polar bears, and

snapping turtles (carnivores, some secondary, some tertiary)

- Top Carnivore refers to the organism at

the top of the food chain or web. (no known predators)

Scavengers are carnivores that feed on dead animals blowflies, turkey vultures, eagles, seagulls,

ravens.

Omnivores feed on both producers and consumers humans, black bears, red-wing blackbirds

Each step in this series of feeding relationships is known as a trophic level. End of lesson #1 Please complete the crossword puzzle in your homework booklet

Food Chains Lesson #2

A sequence of organisms through which energy is passed

tertiary consumes secondary

secondary consumes primary

primary consumes producer

producer converts energy from the sun.

Energy is passed from sun, producer, to primary, to secondary to tertiary!

Do not copy

Producer

wild rice

Primary Consumer

minnows (that look suspiciously like goldfish here)

Secondary Consumer

northern pike

Tertiary Consumer

eagle

Producers and consumers are linked together in food chains

Food Webs

Because animals typically feed on more than one type of organism, food chains become connected in a complex relationship known as a food web. The arrows show how the sun’s energy flows through the ecosystem from the sun, to producers, to consumers.

Key: 1)algae 2) zooplankton 3) bacteria 4) water strider 5) largemouth bass 6) mosquito larva 7) damselfly naiad 8) bluegill 9) tadpole 10) predaceous diving beetle 11) giant water bug 12) crayfish 13) caddisfly larva 14) water flea 15) cyclops 16) rotifer

An example of how food-webs can get very

complex!

What Eats What? p.10 in your text.

Create 12 pieces of paper each with the name of one of the following organisms:

Grass

Ruffed Grouse

Bunch Berries

Grasshopper

Common Raven

Red-Tailed Hawk

Willow Tree

Cotton Tailed Rabbit

Bacteria/Fungi

Squirrel

Maple Seeds

Fox

• Create four food chains, 3 links each. End of lesson 2

Do BLM 1-2, 1-4, Analyzing food chains, and Check your understanding

Ecological Pyramids p. 17 in your textbook

Energy is lost between each link in a food chain. Much (almost 90%) of the potential energy at each level never reaches the next level

Where does the energy go?

Some of the energy that enters a food chain is used as each organism carries out its life functions. This energy is obtained through the 'burning' or breaking down of food molecules. Thermal energy (heat) is produced as a result of the burning of these food molecules. More than half of the energy from each food molecule is lost as heat. Only about 10% of energy at each trophic level is available to pass on to the next level.

Ecological pyramids

3 types: (we will focus on the 3rd)

Pyramid of numbers (p.14 in your text) Where the number of organisms are counted

(producers, primary consumers, secondary consumers etc)

We will find the number of producers is the largest, then primary consumers, then secondary consumers

The higher trophic levels in the food chain have less

energy available to them, therefore there are fewer of

them.

Pyramid of energy flow (p.17 in your text)

The chemical energy that flows through an each trophic level is measured

Again, the higher trophic levels in the food chain contain less energy

Pyramid of Biomass (living and recently dead

biological matter) p. 16 in your textbook

It is possible to estimate the mass of all the organisms living in a given area or ecosystem. This estimation is known as the biomass.

If the mass of the producers and each type of consumer is recorded, a pyramid can be constructed showing that the biomass of the producers is generally far greater than that of the consumers.

The most basic way for energy or biomass to be passed through trophic levels of an ecosystem is for an organism from one trophic level to eat an organism from a lower trophic level

Symbiotic relationships

These are special relationships in which two organism live in close association with each other in order to benefit at least one of them.

Symboiotic relationships do not involve one species “eating” another (at least not completely)

3 common types of Symbiotic

Relationships 1. Mutualism

In this relationship both organisms benefit from their association

Ex termites have micro-organisms living in their digestive tracts to help them break down cellulose. In return the termites body provides the micro-organisms a place to live, and food.

2. Commensalism

In this relationship, one organism benefits from the relationship, while the other is not affected (ex. Pilot fish live within the body of sharks. The pilot fish eat the scraps left-over from the shark’s feeding. However the sharks are neither helped, nor hurt by the pilot fish.

3. Parasitism

In this relationship, one organism (the parasite) benefits while the other organism (the host) is harmed or killed (ex. Tapeworms attach to the intestines of host organisms and absorb the digested nutrients of the host, causing harm to the host).

End of lesson #2

The Cycles of Life p. 46 in your textbook

Nutrients: any chemical that is essential to living things (ex. Carbon, Oxygen, Nitrogen, Iron, Phosphorus, and Zinc etc.)

Biogeochemical Cycles: are the processes by which nutrients move through organisms and the environment. These cycles are essential to the stability of an ecosystem because nutrients often need to be ‘converted’ into different forms so that all of the organisms in an ecosystem can use them.

The Carbon Cycle (read p. 43-51 for clarifications)

The carbon cycle is the flow of carbon through an ecosystem from the atmosphere to organisms, and back to the atmosphere.

The cycle consists of two phases:

Photosynthesis

Cellular Respiration

see p. 46 in your textbook

During photosynthesis, the energy of the Sun is used to convert carbon dioxide (inorganic) into glucose (organic). Plants then change glucose into other types of carbon compounds (carbohydrates). When animals eat plants and algae, the carbon compounds are converted into glucose. The glucose is then converted into carbon dioxide and energy through cellular respiration.

Copy the diagram from page 46 into your notebook rather than trying to copy this one!

Photosynthesis, the 1st phase :

6H2O + 6CO2 + nrj C6H12O6 + 6O2

water + carbon dioxyde + energy glucose + oxygen

Photosynthesis occurs in plants!!

If carbon is taken from the atmosphere (CO2) and inserted into the food chain, why does the earth not run out of CO2?

Cellular respiration, the second phase :

C6H12O6 + 6O2 6H2O+ 6CO2 + nrg glucose + oxygen water carbon dioxyde + energy

Cellular respiration occurs in the mitochondria of animals!!

Cellular respiration and hotosynthesis are opposite reactions!

• What do organisms, like humans, use to make energy?

• Oxygen and carbohydrates.

Oxygen Cycle

The cycling of oxygen is linked to the carbon cycle

oxygen is released during

photosynthesis

oxygen is used during respiration

Did you know… p. 50!

Much of the carbon cycle takes place in aquatic ecosystems. The world’s oceans and lakes hold over 50 times as much carbon dioxide as does the atmosphere. See figure 2.7 on page 50 and put it into your notes.

assignment: p. 51 #1-5

BLM 2-8 Follow that Carbon Molecule

BLM 2-p Matching Carbon Terms

Answers to BLMs

Carbon cycle disruption p.47

If the volume of CO2 produced by cellular respiration ≠ the CO2 absorbed by photosynthesis, the carbon cycle will not be in balance

We know that humans produce more CO2

than is absorbed (greenhouse gases, etc). But where do we get all that CO2 ?

During the carboniferous period (millions of years ago) organic materials (ex plants) decomposed under thick layers of sediment.

This process trapped carbon in the Earth and the carbon cycle was in balance.

Humans have tapped into this carbon source (fossil fuels) and are releasing more CO2 into the atmosphere than we are able to absorb unbalanced!!

Greenhouse effect (don’t write)

Between 1850 and 1990, CO2 production from burning of fossil fuels has multiplied by 500 times.

The excess CO2 is released into the atmosphere and the sun’s radiation is trapped

The Greenhouse Effect

What is it? •The greenhouse effect is what happens when heat reflected from the Earth’s surface gets trapped by particular gases; mainly water vapor and carbon.

•It is named so because it is similar to what happens in a greenhouse.

•The trapping of heat by gases is important in maintaining the warm temperatures of our atmosphere; without them the Earth’s temperature would be to cold to sustain life.

•The problem arises when there are too many GHG’s (greenhouse gases) in the atmosphere.

How Does the Heat get Trapped? •Short-wave radiation (from the sun) passes through the atmosphere

•Some of the radiation is reflected from the Earth’s surface and becomes long-wave radiation (basically, visible light becomes heat)

•Some of the heat escapes the atmosphere and GHG’s, but some is trapped!

•The amount trapped depends on how many GHG’s are present in the atmosphere

How does Carbon end up in the

Atmosphere? (as CO2)

Naturally:

- Volcanoes, Hot springs, Geysers

Technology/Human Based:

- Burning of Fossil Fuels, Industrious outputs (smoke stacks), burning and cutting down trees and vegetation

While CO2 does end up in the atmosphere naturally, humans contribute 130 times more into the atmosphere than natural processes! CO2

emissions have increased 35% since the beginning of the Industrial Age.

The nitrogen cycle (N2)

essential elements : C, O2, H2, and N2

Nitrogen is used for the construction of proteins, DNA and other biological molecules in cells

Organisms can absorb/eat C, O2, H2

directly from the atmosphere.

Ex water, gases, etc

(do not write) The nitrogen cycle is more complex then the C and O2 cycles because atmospheric N2 is usually non-reactive and must constantly be converted

Do not write The atmosphere is 80% nitrogen gas (N2),

organisms cannot directly absorb it in that form.

To absorb atmospheric nitrogen (N2), it must be “fixed” or linked to other elements nitrogen compounds

Ex: NH4, NO3…

Plants absorb nitrogen compounds (NO3, NH4) with their roots…

Organisms (animals) eat the plants or eat organisms that eat plants

This way organisms receive the nitrogen necessary for their diet

Plants absorb

nitrogen

compounds

Rabbits eat

plants

Tigers eat rabbits

(which now have

nitrogen)

How is nitrogen (N2) converted to

nitrogen compounds?

Nitrogen Fixation

is done by nitrogen-fixing bacteria that live in soil or water.

These bacteria (ex Rhizobia) take N2 from the atmosphere and convert it into usable nitrogen compounds.

Decomposition

Another source of nitrogen compounds comes from waste products or dead organisms which are being decomposed into ammonia (NH4) by decomposers

Plants absorb nitrogen compounds from these 2 sources (nitrogen fixing bacteria and decomposers)

Nitrification Ammonia (NH4) which comes from

the decomposition of dead organisms can be converted back into nitrogen compounds (NO3) by nitrifying bacteria.

Denitrification Denitrifying Bacteria complete the

cycle and convert nitrogen compounds (NH4,NO3) back to nitrogen gas (N2).

N2 atmosphere

Nitrogen compounds

Nitrogen fixation

Plants absorb

nitrogen compounds

Nitrogen compounds in soil or water converted back to N2 gas Primary

consummers

Secondary

consummers

Waste and dead

organisms

Ammonia NH4

Denitrification

nitrification

Biogeochemical disturbances

These cycles (C, O2, N2) are usually needed to maintain an ecological balance

However, human activity and natural events can upset the balance of these cycles.

What are some natural events that would affect these cycles?

Because Nitrogen is a limiting factor, if all of a sudden there is an abundance in Nitrogen, some plants are able to explode in population very quickly.

Eutrophication is the build-up of nutrients in an aquatic ecosystem.

How does this happen?

- run-off from nitrogen using fertilizers

- human wastes and sewage

- local lawn fertilizers

How does this affect an aquatic ecosystem?

Eutrophication of Nitrogen Run-off from various sources (previous slide) gets

into an aquatic system, eg: a pond/lake

Since nitrogen is no longer a limiting factor, algae is able to grow aggressively, and blanket the top layer of water

Now, the plant-life below the surface cannot get any sunlight and cannot perform photosynthesis and so they die. This means that they also are no longer producing oxygen

Decomposing bacteria use up even more Oxygen to break down the dead plants, which means that there is very little dissolved oxygen left in the water

Any other organisms that need oxygen to live; fish etc… start to die because they cannot breathe!

Algal Blooms (don’t write) These flare-ups of algae

are called algal blooms

and are a large concern

for environmental officials

This phenomenon can occur in salt or freshwater, and is currently a problem off the west coast of Europe

What does this mean for the fishing communities that rely on marine biota for food and trade?

Algal blooms (do write)

A population of algae due to increased levels of nutrients (mainly nitrogen) in an aquatic ecosystem

Algal blooms are caused by blue-green algae also known as Cyanobacteria

Human impact on the nitrogen cycle

Artificial fertilizers, add nitrates

Burning fossil fuels releases nitrogen in the air

Effects on soil Nitrogen saturation – excess nitrogen washes

into streams etc…

Damage tree roots, causes needles to fall, increase in soil acidity

Effects on atmosphere

Nitrogen containing gases dissolve in water in the air, nitric acid is formed, falls as acid precipitation

Effects on Water Ecosystem

Excess nitrogen causes rapid growth of algae and weeds (eutrophication).

End of lesson

Important Definitions Biodegradable: Organic matter that can be

degraded/decomposed by its physiological environment

Eg: The remains of a wolf’s lunch are

decomposed by different kinds of bacteria. This is possible because the remains are organic.

Non-Biodegradable: non-biodegradable substances will not decay/decompose by natural processes of decay

Eg: Plastics, Styrofoam, metal, glass.

Chemicals that have a high persistence are also non-biodegradable.

More Definitions… Toxin: A Poisonous substance produced

by living cells or organisms that is potentially deadly to other organisms. Toxins are mainly used for either predation or defense.

Eg: A snake uses toxins to kill

(predation), while a bee uses toxins to protect themselves (defense).

Coral Snake: Toxin = Predation Bee: Toxin = Defense

Bioaccumulation Def- a process whereby non-

biodegradable substances (usually toxic) collect in the tissues of organisms.

The concentration of the toxic substance increases as we move up the food chain.

When the concentration is high enough, it can cause mutations, sterility or death.

Ex: Grassy Narrows, Ont- aboriginals consume the fish from the river which contain high concentrations of mercury

Bioaccumulation video

bioaccumulation vid.mov

Bioaccumulation Do you know where the term mad hatters

comes from?

Hats used to be made with mercury. Over time, the workers absorbed the mercury into their bodies (bioaccumulation) and started to exhibit crazy or dillusional behaviors…

Giving them the name ‘the

Mad hatters’

Biomagnification

As toxins are stored and passed up the food chain the amount of toxin present in organisms increases as the trophic level increases

Example of Biomagnification (do not write)

•DDT is introduced into an environment through spraying for mosquitoes

•The plants (producers) are able to get the DDT out of their bodies fairly quickly, so the toxin does not build-up very much

•When a fish comes along and eats the plant, it consumes whatever DDT is in the plant; however, it cannot get rid of the toxin faster than it is consuming it, which means that it starts to build-up.

•This build-up continues to get worse as you move up the food chain

•End of lesson

Carrying capacity

Can populations grow forever in an ecosystem?

What would limit this growth?

Carrying capacity is the largest

population of a species that an environment can support.

Time

# o

f su

rviv

ing

org

an

ism

s

A

B C

D

E

Dynamic equilibrium of an ecosystem

Explanation A-B : At the beginning, the population

increases quickly.

C : The carrying capacity is at its max. The # of living organisms varies but generally stays pretty stable. The population is able to handle small variations in the environment. Net growth = 0

D-E : The population decreases. This happens when an ecosystem is affected by some sort of ecological disaster

Ex forest fire, oil spill…

Limiting factors-

*these influence population dynamics*

Some factors are dependant on the density of the population.

Competition : higher the population,

the more organisms will have to compete

for food, shelter, space and reproductive

partners. Competition happens between

Different species or b/w same species.

-- Predation : higher the population

the more predators will be drawn

to that area

Crowding : overpopulation causes stress.

Stress causes animals to become

more aggressive, females may lose or

abandon their offspring.

Mortality rate , birth rate

-- Diseases and parasites : overpopulation facilitates the spread of disease

Some factors are independant on the density of the population.

Temperature extremes : temperatures

that are too hot or too cold can alter the

amount of available food or cause death

-- Drought : reduction of available food and water

-- Fires and floods : can

kill a large portion

of the population

Biodiversity (don’t

write)

What is it? The variation of organisms/species within a given ecosystem, biome, or entire earth

The health of an ecosystem is often determined by the level of biodiversity present

This means that an ecosystem

with 1000 different species would be considered healthier than one of the same size that contained only 100 species

Biodiversity

Means variety of species (fauna and flora) within an ecosystem.

Biodiversity is reduced in extreme conditions:

The arctic, the desert, etc (there a re fewer species able to live in those conditions)

• **The more biodiverse a region is, the less susceptible it will be to changes in the environment, therefore is more sustainable.

Extinct has more than one definition…

When we think of the term “extinct” we usually connect it with an organism that has completely been eradicated from the Earth. However, the term has come to mean several different things

Thus we end up with different ‘levels’ of extinct!

“Quagga” – A subspecies of Zebra The classic “dodo bird”

Extinct: This term is used when every individual of a particular species has died everywhere on Earth

Ex: Dodo bird, mega fauna from the ice ages,

dinosaurs, Red Colubus Monkey, passenger pigeon

Species, historically, have become extinct for a variety of reasons; natural disasters, or being out-competed by more capable organisms. The reason extinction has become such an important topic is because humans have increased the extinction rate drastically, thereby lowering the biodiversity of the whole earth!

Extirpated: this occurs when a species become extinct in a local area, but still exists elsewhere in the world

Ex: The Beluga Sturgeon is extirpated in the

Adriatic Sea, but populations still exist in the Caspian, and Black Seas, greater prairie chicken, grizzly bears

The Philippine Monkey-Eating Eagle that once lived in several dense, mountainous island forests in the Philippines has now been extirpated from several of those islands, and it is estimated that fewer than 200 survive.

Endangered: a population of species that is at risk of becoming extinct/extirpated

Species that are endangered usually become so due to habitat encroachment, slow breeding rates, and specialized niches.

For example; a Raccoon will most likely never become

an endangered species because it is able to live in many different habitats (urban, rural), and it is highly adaptable. However, polar bears are endangered because they rely on a specific environment and food. It is likely that polar bears will become extinct in the near future

Endangered: whooping crane, burrowing owl, Panda (both red and giant).

Introduction and extinction

of a species

Introduced in Australia

for hunting purposes

Multiplied

exponentially

since the rabbit

had no natural

predators

Destroyed

habitats

Ate many types of

plants, which

destroyed other

animal populations

which fed on the

same plants

Caused big

problems for

agriculture

Chemical and

biological methods

were set in place to

decrease the

population size.

Sustainability

The ability to meet the needs of the present generation without compromising the ability of future generations to meet their needs.

Ecosystems are sustainable (one generation does not affect the ability of the next generation to survive)

Indefinite growth of a population is not possible because resources are limited

Sustainability An ecosystem with a high level of

biodiversity is very resistant to disturbances in the environment.

However, if the survival of a key species is jeopardized, the survival of the whole community is also in jeopardy.

Whales, penguins and sea lions in the Antarctic depend on the survival of krill (their main food source)

our impact= sustainability of the future

Humans and sustainability

Humans activities are not sustainable.

We use non-renewable natural resources (less available to future generations)

We produce harmful polluting wastes which enter nutrient cycles and damage productivity of ecosystems