unit 3 - ecology · organisms in an ecosystem that feed on each other, starting with the producer...

Unit 3 - EcologySection 1 - Introduction to the Sustainability of Ecosystems

Watch: “Biology - The Science of Life”

Unit 3 - Ecology 1 / 38

https://www.youtube.com/watch?v=7L7x0BAqWis

What is Ecology?

Ecology is the study of how organisms interact with each other.

Ecological studies can begin at the level of a single organism.

Investigations are designed to determine how the individual interacts withits environment, and how factors in the environment affect its growth,feeding habits and reproduction.


Abiotic and Biotic Factors

Non-living factors or influences on organisms such as amount of sunlight,temperature, and strength of wind are called abiotic factors.

Factors caused by the presence and roles of other living things are calledbiotic factors.


Populations

Organisms usually group with others of the same species. All of themembers of the same species living in the same habitat at the same timeare referred to as a population.

There are three criteria required for a population:

Same species

Same habitat

Same time


Community

On the other hand, the collections of all the populations of all the speciesin a particular area is called a community.


Ecosystems

There are many types of relationships among the many species living in anenvironment (biotic) and the relationships among these organisms and thenon-living (abiotic) components of an environment.

These living and non-living components of a biological community andtheir interrelationships form an ecosystem.


Sustainability

Although there are many advantages of new technology and advancementsto humankind, we have also created many problems such as pollution anddegradation of ecosystems.

Sustainability is the ability to meet the needs of the present generationwithout compromising the ability of future generations to meet their needs.


Definitions:

Food Chain - is a step-by-step sequence linking the differentorganisms in an ecosystem that feed on each other, starting with theproducer and continuing with consumers.

Producers - Are the only organisms in an ecosystem that can makeor produce its own food.

Consumers - Are organisms in an ecosystem that feed on otherorganisms to get their energy.

Detritus - a food chain that deals with decomposers.

Carnivore - eats animal material (ex. wolf).

Herbivore - eats plant material (ex. deer).

Omnivore - eats both plant and animal material (ex. humans, bears).

Decomposers - these organisms feed on dead or decaying matter.

Habitat - the conditions required for the survival of a species.


Watch: “Morning Lesson with Mufasa”


https://www.youtube.com/watch?v=bW7PlTaawfQ

Assignment - Read pages 8 - 13 in your textbook:

pg. 13 # 1 - 5


Extinction in the Modern World

As the human population increases, extinction appears to increase. Therate of extinction is increasing rapidly. The biggest human activities thataffects this rate is:

Deforestation

Pollution


History of Extinction

By examining rocks and fossils it has been revealed that several large-scaledisasters on Earth have resulted in the extinction of many species.

The largest extinction occurred nearly 245 million years ago in whichapproximately 80% of species went extinct.

Scientists believe mass extinctions like that one were caused by asteroidscrashing into Earth creating dust that blocked the light from the Sun, setoff volcanic eruptions and changed Earth’s environmental conditions.


Other Causes of Extinction

Climate changes

Pressure of competition - If a new species enters into an area andeats the same food as another species, the two must compete for thesame food source. The species that is better at this will survive.


Effects of Extinction

The number of species in an ecosystem is described as the biologicaldiversity or biodiversity of an ecosystem.

Because all organisms in an ecosystem are connected in some way, if thebiodiversity is reduced a “domino effect” can result.

The removal of one part from an ecosystem, like the removal of a movingpart from a car, can cause the collapse of an entire food chain.

For example, if a predator went extinct, the population of the prey wouldincrease.


Restoring Balance

How can we restore balance to affected ecosystems?

Reintroduction of species to an area

Place bans on hunting/trapping

Place bans on pesticides


How do we know when these extinction periods occurred?

→ Piles of evidence (largely accomplished independently) in geologicalstrata, radioactive decay and carbon dating methods.


Assignment - Read pages 14 - 15:pg. 13 # 1 - 5

Read pages 16-19:pg. 19 # 1- 3


Classifying Organisms in an Ecosystem

Biodiversity is a measure of the number and variety of species in anecosystem.

When we look at organisms in an ecosystem, we can classify them on thebasis of what they eat.

There are generally two groups: producers and consumers.


Producers

Are the only organisms in an ecosystem that can make or produce itsown food.

These organisms are known as autotrophs (auto - means self and -troph mean food/eat).

They use abiotic factors to produce food. For example, plants use thesun’s energy to make food by the process of photosynthesis. Plantsare the largest group of producers.

However, some bacteria and protists (algae) are also producers.


Consumers

Are organisms in an ecosystem that feed on other organisms to gettheir energy.

Also referred to as heterotrophs (hetero - means other). For example,a deer east grass to get its energy because it cannot make its ownfood.

There are 3 types of consumers.

Carnivore - eats animal material (ex. Wolf)Herbivore - eats plant material (ex. Deer)Omnivore - eats both plant and animal material (ex. Humans,bears)


Consumers continued...

Consumers also come in varying degrees:

A primary consumer feeds on producers (it is 1st to eat/consume)

A secondary consumer feeds on primary consumers (2nd toeat/consume)

A tertiary consumer feeds on secondary consumers (3rd toeat/consumer

And so on and so on...


Food Chains

A food chain is a step-by-step sequence linking the differentorganisms in an ecosystem that feed on each other, starting with theproducer and continuing with consumers.

It shows the flow of energy from one organism to the other so wealways draw arrows pointing to the organism that is receiving thefood energy (doing the eating).

Note: Food chains only include biotic organisms.

Decomposers - these organisms feed on dead or decaying matter. Theyoccur in many spots along a food chain.


Example: Draw a food chain that includes the following:

Grass

Mouse

Cat

Wolf

Label each as either a producer, primary, secondary, or tertiary consumer.


Trophic Levels in a Food Chain

Within an ecosystem organisms may also be classified or grouped on thebasis of a trophic level, which is the position of an organism in the energyflow pyramid of an ecosystem.

In other words, a trophic level states the position of an organism in a foodchain.

For example:

Plants are in trophic level 1 because they are the first biotic organismin a food chain. If a deer eats that plant it would be considered introphic level 2 and so on and so on.


Example Trophic Level Diagram

Trophic Level Category of Organism Organism1 Producer Grass

2 Primary Consumer; herbivore Grasshopper

3 Secondary Consumer; carnivore Snake

4 Tertiary Carnivore; carnivore Hawk

→ Try and construct your own trophic level diagram.

Include 4 - 5 trophic levels.


Types of Food Chains

Generally, there are two types of food chains:

Grazing Food Chain - goes in sequence of a producer → herbivore→ carnivore → top carnivore. Note: a top carnivore is the finalcarnivore in a food chain. It is not eaten by other animals (when it’salive).

Detritus Food Chain - a food chain that deals with decomposers.Note: “Detritus” literally means waste or debris of any kind.


Food Webs

In reality most organisms do not eat just one thing. Each individualorganism in an ecosystem is involved in many food chains. They allinterlock with each other to form a feeding relationship called a food web.

In a basic food chain, we only show producers, herbivores and carnivores.In a food web we can show omnivores because we can show that anorganism eats plants and animals.

→ Try and construct your own food web.

Include at least 3 food chains.


A note on stability:

The most stable ecosystems are those with the greatest biodiversity. Thisis because they have such complex and well-developed food webs thatreduction in numbers or extinction of one type of organism may only havea small effect on the food web.

In general: The lower the biodiversity of an ecosystem, the simpler thefood web and the more vulnerable each organism (and the entire foodweb) is.

Assignment: Read pg. 34 - 35.Complete questions: #’s 2 - 7 on pg. 39


Following Energy Movement in Ecosystems

Every organism within an ecosystem provides energy for other organisms.Food chains are a way of showing a step-by-step sequence of who eatswhom in an ecosystem; i.e. the flow of energy in an ecosystem.

Every time energy is transferred within an ecosystem, some of the energychanges form. For example, some of the energy from the Sun is convertedinto chemical energy by plants as they photosynthesize. Animals, in turn,rely on the chemical energy (food) produced by plants to live.


Limits on Energy Transfer

It is true of all food chains that the farther up the chain you travel, theless energy is available. In every ecosystem, there is less energy availableto secondary consumers than there is to primary consumers. Why?

Laws of Thermodynamics

1st Law: states that although energy can be transformed (changed)from one form to another, it cannot be created or destroyed.

2nd Law: states that during any energy transformation, some of thenervy is converted into an unusable form (mostly in heat energy)which cannot be passed on.


Limits on Energy Transfers and the Number of Trophic Levels

→ In general, the overall loss of energy at each step sets a limit on thenumber of trophic levels in a food chain at about five. In most ecosystems,there wouldn’t be enough energy to support a higher-level consumer.

Because of this “loss-of-energy” trend, we can represent energy in anecosystem in the shape of a pyramid. There are three main pyramids wewill use to represent important characteristics of ecosystems.


Pyramid of Energy

This represents the approximate amount of energy available at eachtrophic level. This graph is only truly useful when compared to the nexttwo graphs: pyramid of numbers of biomass.


Pyramid of Numbers

A pyramid of numbers can be drawn by counting the number of organismsat each trophic level in an ecosystem. There are often many exceptions tothe overall shape of this graph. For example, many tiny aphids may befound feeding off a single plant.


Pyramid of Biomass

Another useful way to represent an ecosystem is through a pyramid ofbiomass. To make such a pyramid, the dry mass of the dry tissue in theplants or animals is measured and graphed. In this type of pyramid, it israre that the graph of biomass is not a regular pyramid.


Assignment: Read pg. 36 - 38.

Complete questions: #’s 2 - 7 on pg. 39 (from before the break)Complete questions: #’s 8 - 11, 14 on pg. 39

Review: pg. 46 #’s 1 - 9

End of Section 1 - Summary of Assignment Questions:

pg. 13 #’s 1 - 5pg. 19 #’s 1 - 3pg. 39 #’s 2 - 11, 14Review, pg. 46 #’s 1 - 9


unit 3 - ecology · organisms in an ecosystem that feed on each other, starting with the producer...

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