1. LECTURE #2 How Ecosystems work
Unit 8: Ecology

2. The ultimate source of energy on earth is the sun
The ultimate source of energy on earth is the sun. We cannot use the sun’s radiant energy directly to power our cells however.

3. The sun’s energy must be transformed by
producers (photosynthesis) into a usable
form.
Review from last semester: What is the name of the ‘food’ that they make??

4. This usable form (glucose) is then passed up through whatever feeding relationships exist in the ecosystem.

5. Nature has 3 basic ‘job descriptions’
Job #1 Producer- organisms that first capture energy Examples: Plants, some kinds of bacteria, blue-green algae What do producers make? Answer: Energy storing molecules
How do they trap the sun’s energy? Through what process? What is that process similar to in animal cells?

6. Producers are also known as autotrophs; organisms who make their own food.

7. Primary productivity
the rate at which
organic material is
produced by
photosynthetic
organisms in an
ecosystem.
What factors affect primary productivity?

8. Factors that affect the rate of photosynthesis
Amount of sunlight
Amount of Carbon Dioxide
Amount of Water
Temperature

9. Ecological Importance -
Producers make up the base of all feeding relationships on earth!
The producers support all other organisms on earth by providing them directly or indirectly with the energy they need to run their cells.
Without producers, life wouldn’t be possible on earth.

10. Job Description #2 Consumer
Consumers – organisms that consume plants or other consumers to obtain the energy necessary to build their molecules.

11. Consumers are also known as heterotrophs; organisms that get their energy by consuming other organisms.

12. Are these guys autotrophs or heterotrophs?

13. Trophic Pyramid- A graphic organizer that shows the feeding relationship of groups of organisms, and the distribution of biomass or energy among different trophic levels in a given ecosystem.

14. Trophic Level – a group of organisms
that have the same source of energy.
This is represented by a step in a food chain.
Food Chain - the path of energy through the trophic levels of an ecosystem.

15. Marine Food Chain
Arrows point in the direction that the energy is moving.
Note to student: Food chains are oversimplified. In most ecosystems, organisms often occupy more than one trophic level.

16. Food web - a network of interconnected food
chains in an ecosystem.
Food webs are a much better representation of feeding relationships in ecosystems because they show that organisms may feed at multiple trophic levels.

17. Marine Food Web

18. A Food Web Describes the Way Energy is Transferred Within an Ecosystem
Ecology
9/18/2018
A Food Web Describes the Way Energy is Transferred Within an Ecosystem
G. Podgorski, Biol. 1010

19. How trophic levels are organized
The 1st Tropic
Level is made up
of Producers
This is the base of the pyramid.
There is more
available energy at
this level than any
other.

20. Tropic Level 2 is made up of Primary Consumers; organisms that feed
exclusively from
The 1st tropic level.
Herbivores –
Animals that eat
plants or other
Primary producers.
Examples - elk, deer, rabbit

21. Tropic Level 3 is made up of organisms known as Secondary consumers
Tropic Level 3 is made up of organisms known as Secondary consumers. Carnivores - Animals that eat other animals. Examples – tigers, wolves, snakes

22. What do you call an organism that eats plants and animals?
Omnivore –
Organism that eats
plants and other
animals.
Examples – humans,
bears (except polar
bears), pigs

23. 4th trophic level - composed of
carnivores that consume other
carnivores.
These organisms are known as tertiary (3rd order) consumers.

24. How many Trophic Levels does an Ecosystem Typically Have?
It is very rare
for an ecosystem
to have more than
four trophic
levels.
Why do you think
that is?

25. Answer: There is hardly any energy left once it passes up through the 4th trophic level.
The amount of available energy limits the number of trophic levels in an ecosystem.

26. Job #3 Recycling Crew Decomposers – organisms that cause decay.
Ecological Importance-
Decomposition releases
nutrients back into the
environment to be
recycled by other
organisms.
Examples: Bacteria and Fungi

27. Decomposers
get energy from all
trophic levels.
Everything dies
eventually, right?

28. These guys also help recycle waste
Detritivores-
Organisms that feed
on detritus, or
organic waste .
Examples- worms, millipedes, vultures

29. Celebrating Rot and Decay - Detritivores
Ecology
9/18/2018
Celebrating Rot and Decay - Detritivores
Energy isn’t transferred only upwards between trophic levels.
Detritovores use the energy available in dead organisms and allow recycling of essential nutrients in ecosystems.
G. Podgorski, Biol. 1010

30. Take 2 minutes to summarize what you have learned about the three ‘Job Descriptions’ on earth and how they are interdependent on one another.