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Announcements &
Assignments
Lecture
Objectives
Web Resources
Matter &
Energy
Energy
Producing
Reactions
Energy Using
Reactions
Energy
Flow
Lecture
Activity
Food
Webs
Decomposition
&
Matter Cycling
Greenhouse
Effect
Lecture
Syllabus
IB
100/101 Home
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Text Readings in Life, Lewis et al.
Chapter 6, The Energy of Life, pg. 87-101
Chapter 44, Communities and Ecosystems, pg. 873-885
Chapter 46, pg. 916-919
The "Reviewing Concepts" boxes are valuable summaries of
the main
ideas in these sections of the text.
You have open access (no log-in or password needed) to
instructional
materials on the Text web site. Select the text
chapter you want and
use the links to the e-learning modules or other available materials.
There is also a collection of study materials called the "Essential
Study Partner" that you may find useful.
Web Crossing
You may also ask questions and see answers to your
classmates'
questions in Web Crossing in the "Talk to Carl and Ed" discussion.
Objectives
The content of today's lecture will help you
complete this
assignment:
After studying this material you should be able
to:
- Describe the means by which autotrophs and
heterotrophs obtain
energy and matter from their environment.
- Describe the roles of primary producers, herbivores,
carnivores, and
decomposers in the energy flow and nutrient cycling of an
ecosystem.
- Explain how the concepts in the table below play an
integral part in
the growth and reproduction of individuals and the energy flow and
nutrient cycling of an ecosystem.
| Photosynthesis |
Respiration |
Biosynthesis
(Anabolism) |
Net Primary
Production |
| Biomass |
Decomposition |
- Define and explain the distinction between the terms
"energy flow"
and "nutrient cycling" in an ecosystem.
- Apply the terms "energy flow" and "nutrient cycling"
to an
explanation of the "energy pyramid" or the concept of "the rule of
tens."
- Describe the role of each of the concepts listed in
objective #3 in
the global carbon cycle.
Web Resources
Energy = ability to do work, to change or move matter
Matter = chemicals, molecules
Life is made up of energy and matter
What are you made of?
Where does your energy and matter come from?
How do you use it?
- Anybody eat Cheerios for breakfast?
- What about a Breakfast burrito??
- Nutrition Facts listing on food labels
indicates
nutrients that address today's health concerns.
- Overview of Chemical Digestion. Figure: Lewis et al., Life, Fig. 38.11, pg.
751
- METABOLISM = all the biochemical
reactions within cells that
acquire and use energy.
- CATABOLISM (degradation) =
metabolic reactions that break
down large molecules into smaller ones, releasing energy.
* The energy which isn't released as heat is stored temporarily in a
high
energy molecule called ATP (adenosine triphosphate) until it is
required. Figure: Lewis et al., Life, Fig. 6.9, pg. 94
- ANABOLISM (biosynthesis) =
metabolic
reactions that use
energy to synthesize new compounds.
* A typical adult uses 2 billion ATP
molecules a minute! Figure: Lewis et al., Life, Fig. 6.9, pg. 94
- Human energy and the dietary Calorie.
The energy
intake of humans in the form of food is often expressed in dietary
Calories (kilocalories).
Reactions that provide the
energy and chemical compounds for living organisms
Photosynthesis = how plants
use light as an energy source to make sugars from
carbon dioxide
| CO2 + |
H2O + |
--- |
Light
Energy |
---> |
Simple
Carbohydrates
(Sugar) |
+ O2 |
(Cellular) Respiration = how
plants and animals breakdown sugars to provide energy for the chemical
reactions in their bodies
| O2 + |
Simple
Carbohydrates
(Sugar) |
----> |
Heat + |
Usable
Chemical
Energy
(ATP) |
+ CO2 |
+ H2O |
- These reactions are COUPLED to TRANSFER energy from
the sun to
chemical form. This energy transformation sustains all life.
- Photosynthesis
converts light energy into chemical energy (sugar).
- Respiration converts one
form
of chemical energy (sugar) into another form of chemical
energy (ATP, a chemical that provides a smaller packet of
energy than sugar)
- In the process CARBON is CYCLED from the abiotic
environment to
living organisms and back to the abiotic environment:
* Plants take in
carbon
dioxide from the atmosphere during photosynthesis.
* Plants use carbon
dioxide as a building block to make sugar.
* Sugar provides the
energy and carbon-based materials to make new plant parts.
* Animals consume
plants and use the energy and carbon-based materials to build their own
bodies.
* Plants and animals
release carbon dioxide to the atmosphere during respiration.
* The cycle repeats.
Figure: Lewis et al., Life, Fig. 6.2, pg. 89
- The chemical reactions that transfer energy are
inefficient. Only a
fraction of the energy stored in nutrients is used by cells; the rest
is
dissipated as heat.
How do organisms use energy
and chemical compounds produced by photosynthesis and respiration?
Biosynthesis = using simple organic compounds to make
more complex compounds
Lewis et al. use the term anabolism;
see Figure: Lewis et al., Life, Fig. 6.9, pg. 94
Simple
Organic
Compounds |
+ Minerals
+ |
Chemical
Energy
(From
Respiration) |
---> |
Complex
Organic
Compounds |
|
Simple
Carbohydrates |
|
------> |
|
Complex
Carbohydrates |
Fatty Acids &
Glycerol |
|
------> |
|
Fats &
Lipids |
| Amino
Acids |
|
------> |
|
Proteins |
| Nucleotides |
|
------> |
|
DNA &
RNA |
- Respiration provides
the energy to make new, more complex organic compounds which allow the
organism to
grow and reproduce.
Energy flow: Community trophic
level relationships
- Energy
capture by Autotrophs
("self-feeders" or "producers", for ex., plants)
underpins communities by providing energy for Heterotrophs
("consumers", for ex., animals).
- Producers extract energy and matter
from
the non-living
environment (light, inorganic nutrients and
minerals in the soil).
- Consumers obtain energy and nutrients by eating
other organisms.
- Decomposers are consumers that break down
dead organisms and
organic waste to obtain nutrients. As they digest their food, inorganic
nutrients are released which plants take up from the soil.
- A characteristic of
life is that energy is required to
maintain
organization at all biological levels. Life remains ordered and complex
because of the constant influx of energy from the sun.
- The energy made available by these producer
organisms
to consumer
organisms is called NET PRIMARY PRODUCTION (NPP)
Energy "Fixed"
by Photosynthesis
(Gross Primary
Production) |
MINUS |
Energy "Released"
by Respiration
(Heat) |
Lecture activity
1. Get together in small groups.
2. Each person PRINT and SIGN your name on your
paper.
3. What did you have for your last meal? (Hopefully,
breakfast!)
4. Was it an autotroph or heterotroph?
5. How many trophic levels are there between you and
the sunlight (your
ultimate energy
source)?
6. What trophic level do you belong to?
7. What limits the number of trophic levels?
Food webs and efficiency of
energy transfer
- Figure of Food Web: Lewis et al., Life, Fig.
44.10, pg.
876
- Food webs describe the relationships between the
eaters and the
eaten in communities. They represent the pathways that nutrients and
energy follow as they move through a succession of plants, grazing
herbivores, and carnivorous predators. Producers sit at the bottom of
the food web and are in the first trophic level or
link in the
food chain. Consumers (herbivores) in the second trophic level eat the
producers, and consumers in the third trophic level eat the consumers.
No organisms prey on the carnivore sitting at the highest trophic
level.
- Most food chains only have three links (eg., grass
-> cow ->
cowboy).
Energy flow through an ecosystem, showing four
trophic
levels. Figure: Lewis et al., Life, Fig. 44.11, pg.
877
- Organic compounds synthesized by primary producers
are stored in the
form of biomass (the total dry weight of individual
organisms,
populations, trophic levels, or entire ecosystems)
- Moving upwards through the trophic levels, the
numbers and biomass
of organisms decrease and the size of the organisms increase. The
larger
numbers of small organisms at the lower trophic levels collectively
have
a much larger biomass than the smaller number of organisms at the upper
levels.
- The Rule of Tens. Only 10% of
the
energy in a trophic level
is passed on to the next trophic level. The 90% energy loss at each
trophic level goes to the metabolic needs of the
organisms at
that level. These needs include the energy required for motion,
breathing, eating, growth, and reproduction. Energy is
lost as heat, because the chemical reactions underlying these processes
are inefficient.
- Energy flow through an ecosystem, showing 10% rule
of
energy
transfer. Figure: Lewis et al., Life, Fig. 44.11, pg.
877
- Energy Pyramid showing
inefficiency of energy
transfer.
Decomposition and matter
cycling
- What if portions of an organism remain uneaten, or
if
a plant or
animal dies naturally?
- Decomposers (e.g., bacteria and
fungi) use the dead organic matter as their food. As they digest their
food, heat is released--just like other consumers.
- Eventually, all stored energy is dissipated as
heat.
Ecosystems
require continual energy input from the sun to function indefinitely.
- Decomposers play a critical role in food webs
because
they break
down the organism's organic molecules to nutrients or simple molecules
such as carbon dioxide and water. They recycle the finite supply of the
essential elements of life (e.g., carbon, nitrogen, phosphorus) making
them available for plants to take up once more.
- Since no significant amount of new matter comes to
the Earth from
space, this recycling of matter is vital for the continuation of life
on
the planet.
- Three biogeochemical cycles:
The Greenhouse Effect:
Consequences of human modification of the Carbon cycle
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