1. The midterm exam will cover lectures 5-10 and include questions testing definitions, short answers, and explanations. Sample questions could ask students to define terms like species and population dynamics, explain the difference between epidemiological measures, or describe a figure showing an ecological concept. 2. The exam will be held on November 5th during class time and last 1 hour and 20 minutes. It will consist of 4 out of 6 total questions. 3. Students are reminded to submit their group exercise reports by October 26th, with presentations on the group work occurring on October 31st.

1. What are we going to learn today?
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 Fundamentals of ecosystems
 Food chains & webs – predator/prey cycles
Lec 9; MrL
Fundamental Concepts of Ecosystem
and Ecological Succession

2. Fundamentals of ecosystems
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 What is an ecosystem?
Life is sustained by the interactions of many organisms
functioning together, interacting through their physical and
chemical environments – called ecosystem. Example: a forest
ecosystem.
 Ecosystem Structure (what are there?)
An ecosystem has two major parts:
 Nonliving: physical-chemical environment, including
the local atmosphere, water, and mineral soil (on land) or
other substrate (in water)
 Living: called the ecological community, is the set of
species interacting within the ecosystem
Lec 9; MrL

3. 3
 Ecosystem Processes (how it works?)
Two basic kinds of processes must occur in an ecosystem:
 a cycling of chemical elements - as we learned in the last
lecture
 a flow of energy – will be described later
 These processes are necessary for all life, but no
single species can carry out all necessary chemical
cycling and energy flow alone. That is why
sustained life on Earth is a characteristic of
ecosystems, not of individuals or populations.
Lec 9; MrL

4. 4
Lec 9; MrL
Food chains & Food webs

5. 5
Food chains: the linkage of who feeds on whom
The more complex linkages are called food webs
A trophic level consists of
all organisms in a food
web.
Green plants, algae, and
certain bacteria produce
sugars through the process
of photosynthesis, using
only energy from the sun
and carbon dioxide (CO2)
from the air. They are
called autotrophs, and
are grouped into the first
trophic level.
All other organisms are
called heterotrophs. Of
these, herbivores—
organisms that feed on
plants, algae, or
photosynthetic bacteria—
are members of the
second trophic level.
Carnivores, or meat-eaters, that feed directly on
herbivores make up the third trophic level.
predator/prey cycles
Decomposers, those that feed on dead organic
material, are classified in the highest trophic level in an
ecosystemLec 9; MrL

6. An Oceanic Food Chain and Web
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• In oceans, food webs involve more
species and have more trophic levels
than in a terrestrial ecosystem.
• In a open-ocean ecosystem (Figure
5.6), microscopic single-cell planktonic
algae and planktonic photosynthetic
bacteria are in the first trophic level.
• Small invertebrates called zooplankton
and some fish feed on the algae and
photosynthetic bacteria, forming the
second trophic level.
• Other fish and invertebrates feed on
these herbivores and form the third
trophic level.
• Some fish and marine mammals, such
as killer whales, feed on the predatory
fish and form higher trophic levels.
Lec 9; MrL

7. A Terrestrial Food Web
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• The first trophic level, autotrophs,
includes grasses, herbs, and trees.
• The second trophic level, herbivores,
includes mice, an insect called the pine
borer, and other animals not shown here.
• The third trophic level, carnivores,
includes foxes and wolves, hawks and
other predatory birds, spiders, and
predatory insects.
• People, too, are involved as omnivores (eaters of both plants and animals),
feeding on several trophic levels. In this people would be included in the fourth
trophic level, the highest level in which they would take part.
• Decomposers, such as bacteria and fungi, feed on wastes and dead organisms of
all trophic levels. Decomposers are also shown here on the fourth level.
predator/prey cycles
Lec 9; MrL

8. References for today’s lecture
BOTKIN, D. B. & KELLER, E.A. 2011.
ENVIRONMENTAL SCIENCE: EARTH AS A LIVING
PLANET (Eighth Edition). JOHN WILEY & SONS, INC.
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Lec 9; MrL

9. ANY
QUESTION?
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Lec 9; MrL

10. Quiz 2: Env 107 (section 38)
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Date: 29-10-2015
Time: class time (please don’t be late)
Place: Room no. NAC 202
Syllabus: lectures 5-8
Marks: 20
No. of Questions: 20
Duration: 20 min
Question type: MCQ, true/false

11. Group exercise report and presentation
Lec 9; MrL
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 Report submission: 26/10/2015 (submit hard copy
at SAC 704 to me within 4.10pm and soft copy within
11.59pm to my email)
 Presentation is on 31/10/2015 (all groups)

12. Mid term-1 exam
 Mid term exam
 Date: 5/11/2015
 Time: Class time (11am)
 Syllabus: Lectures 5-10
 Question type: Definition, short question, explanation.
 No MCQ, True/false
 Total 4 questions need to answer out of 6
 Exam duration: 1 hr 20 minutes
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13. Sample question for Mid-1
Lec 9; MrL
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1 a) Define species, population dynamics, and crude growth rate. (1+1+1)
b) Write the difference between incidence, prevalence and life expectancy at birth. (3)
c) Explain the figure below: (4)