College of Arts and Sciences Education

BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

Course Information – see download course syllabus in the Black Board LMS

CC’s Voice: Hello biologist! Welcome to this course BIO 212/L

GENERAL ECOLOGY

Course Outcome: At the end of the course, you are expected to:
1. Integrate ecological concepts and principles to current environmental issues and practices.
2. Apply the ecological concepts in developing solutions to anthropogenic activities affecting the
environment.
3. Explain the importance of studying ecological concepts and principles especially in policy-
making towards protection and preservation of our environment
Let’s begin!

ECOSYSTEM ECOLOGY
Big Picture

Week 3-4: UNIT LEARNING OUTCOMES (ULO): At the end of the unit, you are
expected to:

a. Define what is an ecosystem.

b. Differentiate the types of ecosystem
c. Identify the components of an ecosystem
d. Describe the biota of terrestrial biomes
e. Describe the biota of freshwater ecosystem

Big Picture in Focus: ULOa-ULOc. Explain some basic concepts and

principles related to ecosystem ecology
Metalanguage
In this section, you will encounter certain ecological terms as we study basic
principles and concepts related to ecosystem ecology. Below are the operational meaning of
these terms that are relevant in this particular chapter.

1. Ecosystem. This refers to the basic functional unit of organism and their environment
interacting with each other and with their own components.
2. Biotic- Refers to living organisms.
3. Abiotic- Refers to non-living organisms.

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

Essential Knowledge

To perform the aforementioned big picture (unit learning outcomes) for the third (3)
and fourth (4) weeks of the course, you need to fully understand that the basic unit of
ecology is the ecosystem hence, as an ecologist you should have a commendable knowledge
about this concept.

Introduction

The word ecosystem consist of two words namely-eco which implies the
environment and system implies an interacting, inter-dependent complex. The concept of
ecosystem was first introduced by Tansley (1935).He defined it as a system resulting from
the interaction of all the living and non living factors of the environment. Meanwhile,
according to American ecologist, E.P. Odum, ecosystem is a basic functional unit of
organism and their environment interacting with each other and with their own components.
Molles (2016), said that an ecosystem includes all the organisms that live in an area and the
physical environment which those organisms interact.
Molles, M.C.Jr.(2016).Ecology Concepts and Applications.8th ed.Mcgraw-Hill International

Ecosystem is a major ecological unit. It has both structure and function that is studied
in Ecology. The structure is related to species diversity.The more complex the structure the
greater the diversity of ecosystem. An ecosystem is an open system. It is broad and flexible.
The function of an ecosystem is related to energy flow and material cycling through and
within the system. Some of the major natural ecosystems are forest, grassland, deserts, lakes,
ponds, etc. An ecosystem involves important interactions between biotic and abiotic factors
as shown in Fig. 1

Fig. 1-The biotic and abiotic components of an ecosystem

(Source: https://www.google.com/search?q=functional+groups+comprising+an+ecosystem&client=firefox-
b&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwi5jKiVpvHTAhUBL5QKHRGiAjYQ7AkIVw&biw=1024&bih=489 )

Types of ecosystem

1. Natural ecosystem-this ecosystem operate under natural conditions without any major
interference by man. Examples are: terrestrial ecosystem ( forest, grassland, desert,etc.), and

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

aquatic ecosystem such as freshwater (lotic)-running water like spring, stream, rivers or
freshwater (lentic)-standing water like lake, pond, pool, etc. and marine water such as deep
bodies as ocean or shallow ones as sea or an estuary.

2. Artificial (man-engineered ecosystem)-this ecosystem is maintained artificially by man

whereby addition of energy and planned manipulation, natural balance is disturbed regularly,
e.g. cropland ecosystem.

Fig. 2. Types of ecosystem

(
https://www.google.com/search?q=image+of+structure+of+an+ecosystem&client=firefox-
b&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwj3m96vsvHTAhWBJZQKHVkyCT4Q7AkIRQ&biw=1024&bih=489#q=image+of+structure+of+an+ecosystem&tbm=isch&tbs=rimg:CdjKSjOQNMiCIjgAqrWBT
5hDdlNIjKJVBzYAyNiSXPwSb0QL3X7kX6L4ZZjFWH8PRpIkSOml5_1AWsR5sfMq_1xb5nzSoSCQCqtYFPmEN2EUI1G06omPslKhIJU0iMolUHNgAREz6RNAHlehkqEgnI2JJc_1BJvRBFH7UwhQ2HCXioSCQvdfuR
fovhlEfeJwg1eDtBcKhIJmMVYfw9GkiQRb6iCgHkuyKkqEglI6aXn8BaxHhELDG17syNUPioSCWx8yr_1FvmfNESmGrbXEcEoj&imgrc=U0iMolUHNgC97M:)

Ecosystem structure

There are 3 main biotic components in an ecosystem namely:

1. Producers-also called “photoautotrophs” create food using sunlight energy. They

are “self feeders” –they produce food for all the other organisms. Examples are:
plants, algae and cyanobacteria. The green plant contains chlorophyll that enables
them to photosynthesize.
2. Consumers-also called “heterotrophs” obtain energy through eating other
organisms. They do not possess the green pigment-chlorophyll hence, they cannot
photosynthesize. Examples are herbivores, carnivores, and omnivores.
3. Decomposers-also called “saprotrophs” obtain food through the breakdown of dead
organic matter. They are important in recycling nutrients. Examples are bacteria and
fungi. Some bacteria are chemoautotrophic decomposers-they use a similar process
to photosynthesize which uses energy from oxidation reaction rather than sunlight.
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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

Moreover, a structure of an ecosystem that is composed of biological community

based on its trophic level also includes species number, biomass, life history, distribution in
space, and the quantity and distribution of abiotic factors (non-living materials) such as
nutrient, water, etc., and the range of condition for existence such as temperature, light, etc.

Fig. 3. Components of an ecosystem

https://www.google.com/search?q=image+of+structure+of+an+ecosystem&client=firefox-
b&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwj3m96vsvHTAhWBJZQKHVkyCT4Q7AkIRQ&biw=1024&bih=489#q=image+of+structure+of+an+ecosystem&tbm=isch&tbs=rimg:CWSD36gv4QB3Ijii4JVcChE
iMaaAtRcaMnLf-TEEMhPqD4N3HnFVPzK4nvs9zuv6r3NE6x_1JUHfUjEGbKzqZxBwUnCoSCaLglVwKESIxEXsQOA4XY-8QKhIJpoC1Fxoyct8R0_1s0EKad6xsqEgn5MQQyE-oPgxHZb6Sk5-

Self-Help: You can also refer to the sources below to help you further
understand the lesson:

Molles, M.C.Jr.(2016).Ecology Concepts and Applications.8th ed.Mcgraw-Hill International

Ecosystem structure. Retrieved from https://www.google.com/search?
q=image+of+structure+of+an+ecosystem&client=firefox-
b&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwj3m96vsvHTAhWBJZQKHVkyC
T4Q7AkIRQ&biw=1024&bih=489#imgrc=3VsKIDnEnMJzfM

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

Let’s check

A. LECTURE ACTIVITY

Activity 1. Multiple choice. Choose the best answer.

1. The biological community and the abiotic parts of the environment that affect the
community is called
a. species b. habitat c. niche d. population e. ecosystem
2. A person that study the structure and function of an ecosystems
a. environmentalist c. ecologist e. none
b. conservationist d.forester

For numbers 3-4, use the pictures below

3. Which picture best represents a population? (a. A b.B c.C d.D).

4. Which picture best represents an ecosystem? (a. A b.B c.C d.D ).

5. The driving force in an ecosystem is the (a. sun b.water c.plants d.nutrients).

6. Solar energy is first transformed into chemical energy by the ______ when it enters
an ecosystem (a. producers b.herbivores c.carnivores d.omnivores
e.decomposers).

7. A consumer is __________________.

a.an organism that produce its own food

b.an organism that is nonliving
c. an organism that feed on other organism
d. an organism that convert light energy to chemical energy

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

8. Organism that break down organic matter is called -----------

a. autotroph b. herbivore c. omnivore d. chemoautotroph e. saprotroph

9.The following are heterotrophs except ----------

a. grass b. goat c. carabao d. butterfly e. snake

10.Which of the ff: best explains why nutrient cycle is important in an ecosystem?
a. nutrient cycle is needed by the biotic component of an ecosystem
b. nutrient cycle is needed by the abiotic component of an ecosystem
c. nutrient cycle provides abundant supply of nutrients
d. nutrient cycle can be recycled-can be used over and over again
e. nutrient cycle provide linkage between the biotic and abiotic components of
an ecosystem

Activity 2. UNDERLINE a word or group of words DOES NOT belong to the same concept
and explain (1pt for the answer and 2points for the reasoning)

1. Tansley, Haeckel, Odum, Molles

- Tansley, Haeckel, Odum were scientists that works and studied about the theory of
Ecology, while on the other side Molles is an emeritus Professor of Biology at the
University of New Mexico and he is the author of the book Ecology: Concepts and
Applications
2. producers, consumers, climate, decomposers
- Producers, consumers, decomposers are 3 main biotic components in an ecosystem.
3. spring, lake, ocean, pond, river
- Spring, river, lake, ponds are considered freshwater (lotic and lentic) while sea
belongs to marine water.
4. cropland, grassland, sea, forest, desert
- Cropland, grassland, forest, deserts are all terrestrial ecosystem while the sea
belongs to Aquatic Ecosystem.
5. grass, fungi, algae, trees
-Grass, algae and trees are considered as producers or photoautotrophs while fungi
belong to decomposers or saprotrophs.

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

Let’s analyze

Activity 1. As an ecologist, you should have a deep understanding about our role in an
ecosystem. Hence, I want you to explain thoroughly your answers.

1. What is the role of man in an ecosystem?

-Since ecosystem has many offers to mankind like air, water, nutrient cycle, soil
fertility and many other things that a man needs to survive, in return we have a very
important role,

2. Why must ecosystems be considered systems?

- When we talk about system it refers to a set of things that works together as part of a
mechanism, that’s why Ecosystem can be considered as a system in the reason that.
just like how the system works, ecosystem refers to a set of species that lives in a
given area that interact with each other.

3. What are some factors which you think could affect an ecosystem?
-

In a Nutshell

In this chapter, you were introduced to basic concepts and principles related to
Ecosystem Ecology. Your task is to enumerate important ideas and concepts that were
discussed in this particular chapter. I will supply the first item and you will continue the rest.

1. Biotic factors 6. Marine water

2. Producer 7. Natural Ecosystem
3. Consumer 8. Artificial Ecosystem
4. Decomposer 9. Terrestrial Ecosystem
5. Freshwater 10. Aquatic Ecosystem

B.) LABORATORY ACTIVITY

* Perform Expt. 4-5. Refer to Ecology Laboratory Manual

* Further instructions regarding the procedures in relation to the conduct of
these experiments will be posted through LMS. Check it out!
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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

BB
Big Picture in Focus: ULOd. Describe the biota of terrestrial ecosystems

Metalanguage

Please note that you will also be required to refer to the previous definitions found in
ULOa-ULOc section.

1. Biota.This refers to the animal and plant life of a particular region, habitat, or geological
period.
2. Biome. This term refers to major regional ecological community of plants and animals.
3. Biomass. This is the weight of living material, usually expressed as dry weight per unit
area.
4. Climate.This term refers to the weather conditions prevailing in an area in general or over
a long period.
5. Decomposition.Refers to the breakdown of complex organic substances into simpler ones.
6. Grassland. A large open area of country covered with grass, especially one used for
grazing.
7. Net primary production. This term refers to energy accumulated in plant biomass.
8. Nutrient cycle. It is the pathway of an element or nutrient through the ecosystem, from
assimilation by organisms to release by decomposition.
9. Nutrient. A substance an organism requires for normal growth and activity.
10. Rainforest. A permanently wet forest of the tropics.

Essential Knowledge

Forest ecosystem

Natural and planted forests occupy about 30% of the earth’s land surface (excluding
Greenland and Antarctica). Tropical forest for example account for more than half of the
world’s forest area, and boreal (northern coniferous) account for one fourth. There are two
major types of natural forest namely: old-growth forest: an uncut or regenerated primary
forest that has not been seriously distributed by human activities or natural disasters for 200
years or more. Old-growth or primary forest are reservoirs of biodiversity because they
provide ecological niches for a multitude of wildlife species. The second type is a second-
growth forest: a stand of trees resulting from secondary ecological succession. These forest
develop after the trees in an area have been removed by human activities, such as clear-

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

cutting from timber or cropland, or by natural forces, such as fire, hurricanes, or volcanic
eruption. Forest provide highly valuable ecological and economic services. For example,
through photosynthesis, forest remove CO2 from the atmosphere and store it in organic
compounds (biomass). By performing this ecological service, forests help to stabilize the
earth’s temperature and to slow global warming as part of the global carbon cycle.

Climate and forest ecosystem

Interaction between moisture and temperature is the primary factor limiting the nature
and geographic distribution of forest ecosystems. The gradient of dominant tree forms and
forest types with changing climate is accompanied by changes in the structure and function of
these ecosystems. The combined influence of climate on net primary productivity and
decomposition give rise to a distinct pattern of carbon and nutrient cycling across the
different forest ecosystems. At one extreme, tropical forests possess a large standing-crop-
biomass that ties up great quantities of nutrients. Much of the mineral cycling takes place
between rapid decomposition of litter and the rapid uptake of the nutrients it contains.

Tropical and Subtropical Seasonal Forests and Dry Tropical Forests

Seasonality of rainfall determines the types of tropical forests. Rainforests are

associated with high seasonal rainfall; subtropical seasonal forests experience droughts of
two to four months. Dry tropical forests undergo varying lengths of dry season that end with
a rainy season. Tropical rain forests noted for their enormous diversity of life divide into five
general layers: emergent trees, high upper canopy, low tree stratum, shrub understory, and a
ground layer of herbs and ferns. Conspicuous parts of the rain forest are the lianas or
climbing vines, epiphytes growing up in the trees, and stranglers that grow downward from
the canopy to the ground. Many large trees develop buttresses for support. Horizontally, the
rain forest is a mosaic of continually changing vegetation that adds to its diversity brought
about by disturbance and death of trees. Vertical layering of the strata results when groups of
species of similar mature height dominate a stand. Reflecting this stratification is the
stratification of animal life into six pronounced feeding groups from the canopy down to the
ground layer.

Grassland Ecosystem

Grasslands provide many important ecological services, including soil formation,

erosion control, nutrient cycling, storage of atmospheric carbon dioxide in biomass, and
maintenance of biodiversity. One type of grasslands are the -savannas which are described as
grasslands with woody vegetation. They are characteristics of region’s with alternating wet
and dry seasons. Difficult to characterize precisely, savannas range from grass with

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BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

occasional trees to shrubs to communities where trees form an almost continuous canopy.
The latter grades into woodlands with an understory of grass. All savannas in one way or
another have been altered by humans. The physical structure of savannas is distinct. The
vertical structure is poorly developed, whereas the horizontal –consisting of clumps of
tussock grass, widely spaced shrubs, and trees-is well developed. Savannas support a large
and varied assemblage of herbivores, invertebrate and vertebrate. Seasonality of rainfall
influences productivity and nutrient cycling in savannas. Most production and decomposition
takes place through the wet season. Much of the nutrient pool is tied up in plant and animal
biomass, but nutrient turnover is high, with little accumulation of organic matter.

Nature and structure of grassland

Natural grasslands occupy regions where rainfall is between 250mm and 800mm a
year, but they are not exclusively climactic. Many exist through the intervention of fire and
human activity. Once covering extensive areas of the globe, natural grasslands have shrunk to
a fraction of their original size because of conversion to cropland and grazing lands.
Conversions of forests into agricultural lands and the planting of hay and pasturelands
extended grasslands into once-forested regions. Grasslands vary with climate and geography.
Eurasia has steppes; South America the pampas and the veldt of southern South Africa.
Grassland consist of an ephemeral herbaceous layer that arises from crowns, nodes, and
rosettes of plants hugging the ground above and has three or more sub-layers, the ground
layer, and below-the ground root layer. Depending upon their fire history and degree of
grazing and mowing, grasslands accumulate a layer of mulch that retains moisture, influences
the character of and composition of plant life, and provides shelter and nesting sites for some
animals. A highly developed root layer that makes up more than half of the plant extends to a
considerable depth into the soil. Grassland support a diversity of animal life dominated by
herbivorous species, both invertebrate and vertebrate.

Productivity of grasslands

Productivity varies considerably, influenced greatly by precipitation. It ranges from

400 kcal/m2/yr in semiarid grasslands to 30 times as much in sub humid, domestic, and
cultivated grasslands. The bulk of production goes underground the roots. Grassland evolved
under the selective pressure of grazing. Thus, up to a point , grazing stimulates primary
production. Although the most conspicuous grazers are large herbivores, the major consumers
are invertebrates. The heaviest consumption takes place below-ground, where the dominant
herbivores are nematodes. Most of the primary production goes to the decomposers. Essential
to the cycling of nutrients is mulch. Nutrients are cycled rapidly. A significant quantity goes to
roots to be moved above-ground to the next year’s growth.

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

Self-Help: You can also refer to the sources below to help you further
understand the lesson:

Molles, M.C.Jr.(2016).Ecology Concepts and Applications.8th ed.Mcgraw-Hill International

Molles, Manuel C. Jr. (2019). Ecology. Concepts and Applications.8th edition

Smith,Thomas M. and Smith Robert Leo (2004).Elements of Ecology.5th ed.

Let’s check

A. LECTURE ACTIVITY

Activity 1. Multiple choice. Choose the best answer

1. Biodiversity is greatest in which biome?

a. taiga b. rain forest c. savanna d. polar
2. All the different species of an ecosystem are referred to as:
a. biome b. community c. population d. ecosystem
3. The types and numbers of species in a given area is most greatly determined by the
areas
a. biotic factor b. abiotic factors c. biodiversity d. climate
4. ____________biomes are large, rolling terrains of grasses, flowers and herbs.
a. desert b. grassland c. forest d. forest
5. This word best describes the rainfall in the grasslands.
a. moderate b. heavy c. fair d. none
6. A ---------------- is a kind of grassland that has a mild climate.
a. desert b. savanna c. tundra d. none
7. What does the burning grasses provide in an ecosystem?
a. rich soil that is good for farming c. more trees used for lumber
b. air pollution d. more CO2
8.Which of the following describes the tropical rain forest?
a. hot and humid b. cold and dry c. hot and dry d. warm and humid
9. Which of the following describes the rainfall in the rain forest?
a. very little b. moderate c. year-round d. heavy

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

10. Which of the following is not part of a forest structure?

a. ceiling b. canopy c. understory d. forest floor
11.Which layer of the forest receives the most light?
a. understory c. canopy
b. forest floor d. all layers receives same amount of light
12. Terrestrial ecosystems are based on
a. microclimate c. type of soil
b. diversity of organisms d. vegetation structure
13. Forest ecosystems are usually limited by factors such as
a. water supply c. soil type
b. wind movement d. moisture and temperature
14. Productivity is high in forest if ;
a. nutrient availability is low c. decomposition rate is high
b. high temperature d. low biomass
15. Savannas are grasslands dominated not only by grasses but also
a. shrubs b. herbs c. woody plants d. all
16. The greatest limiting factor in grassland ecosystem is
a. moisture b. soil type c. precipitation d. vegetation structure

Activity 2. Reflection

Your task in this activity is to research the current status of Philippine forest and
discuss the ecological issues affecting our forest ecosystem. In addition, discuss also the pros
and cons of Philippine Govt. Programs that are currently implemented in addressing the
problems that you cited.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

Let’s analyze

Activity 1.As an ecologist, you should distinguish the unique features of the different kinds
of terrestrial ecosystems. Hence, I want you to explain your answers.

1. If tropical forest soils are so nutrient poor, how come they support such a high plant
biomass and biodiversity?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

2. How does structural stratification of a forest affect its diversity of animal life?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

3. What characteristics do all grasslands have in common?

_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

4. Why does the root system assume such importance in the grassland ecosystem?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

5. List the three most important features of your policies for using and managing
Philippine forests and grasslands?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

6. List two questions that you would like to be answered as a result of reading this
chapter

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BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

In a Nutshell

In this chapter, you were introduced to basic concepts and principles related to
Ecosystem Ecology. I want you to summarize the difference between forest and grassland
ecosystems respectively using the following criteria.

CRITERIA FOREST VS. GRASSLAND

1.Humidity ---------------- -------------------

2.Temperature ---------------- -------------------

3.Primary production ---------------- -------------------

4.Structure ---------------- -------------------

5.Kind of plants ---------------- -------------------

6.Kind of animals ---------------- -------------------

7.Rainfall ---------------- -------------------

8.Types ---------------- -------------------

9.Importance ---------------- -------------------

- grasslands provides water catchments, biodiversity reserves, recreational needs and also
the air we breathe. It also provides habitat for human and for animals.

- Forest also helps us in our survival, from the air we breathe to the wood we use for
cooking, it also offers watershed protection, and the tress in the forest also help prevent soil
erosion.

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

We depend on forests for our survival, from the air we breathe to the wood we use. Besides
providing habitats for animals and livelihoods for humans, forests also offer watershed
protection, prevent soil erosion and mitigate climate change.
grasslands provide important services and roles including as water catchments,
biodiversity reserves, for cultural and recreational needs, and potentially a carbon sink to
alleviate greenhouse gas emissions. Inevitably, such functions may conflict with
management for production of livestock products.
B.) LABORATORY ACTIVITY

 Perform Expt. 5. Refer to Ecology Laboratory Manual

 Further instructions regarding the procedures in relation to the conduct of
this experiment will be posted through LMS. Check it out!

Big Picture in Focus: ULOe. Describe the biota of freshwater ecosystem

Metalanguage

Please note that you will also be required to refer to the previous definitions found in
ULOa-ULOd section.

1. Freshwater ecosystem- it refers to flowing waters (lotic) such as streams , rivers and
standing waters (lentic) such as lakes and ponds.

2. Lakes-a large natural bodies of standing freshwater surrounded by land.

3. River- a large natural stream of water flowing in a channel to the sea, a lake, or another
such stream

4. Streams-refers to a small, narrow river

Essential Knowledge

Freshwater life zones include standing (lentic) bodies of freshwater, such as lakes,
ponds, and inland wetlands, and flowing (lotic) systems, such as streams and rivers. Although

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BS Biology
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(082) 300 - 5456 Local 118

these freshwater systems cover less than 2.2% of the earth’s surface, they provide a number
of important ecological and economic services.

Zonation of Life in Lakes – The area where light penetrates to the bottom of the lake, a
zone called the littoral, is occupied by rooted plants. Beyond this is the open-water or
limnetic zone inhabited by plant and animal plankton and fish. Below the depth of effective
light penetration is the profundal region, where the diversity of life varies with temperature
and oxygen supply. The bottom or benthic zone is a place of intense biological activity, for
here decomposition of organic matter takes place. Anaerobic bacteria are dominant on the
bottom beneath the profundal water, whereas the benthic zone of the littoral is rich in
decomposer organisms and detritus-feeders.

Nutrient Input into Lakes- Lakes may be classified as eutropic or nutrient-rich,

oligotrophic or nutrient-poor, acidic and rich in humic material. The type is strongly
influenced by the surrounding landscape in which the lake is situated. Most lakes are subject
to cultural eutrophication, which is the rapid addition of nutrients, especially nitrogen and
phosphorus from sewage, industrial waste, and agricultural runoff.

Flowing Water Habitat-Currents and their dependence on detrital material from surrounding
terrestrial ecosystems set flowing-water ecosystems apart from other aquatic systems. Current
shapes the life in streams and rivers and carries nutrients and other materials downstream.
Flowing water ecosystems change longitudinally in flow and size from headwater streams to
rivers. They may be fast or slow, with stream habitats characterized by a series of riffles and
pools. Organisms well adapted to living in the current inhabit fast-water streams. They may
be streamlined in shape, flattened to conceal themselves in crevices and underneath rocks or
attach to rocks and other substrates. In slow-flowing streams where current is minimal,
streamlined forms of fish are replaced by fish with compressed bodies that can move through
aquatic vegetation and by burrowing invertebrates that inhabit the silty bottom. Stream
invertebrates fall into four major groups that feed on detrital material: shredders, collectors,
grazers, and gougers.

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(082) 300 - 5456 Local 118

River Continuum-Life in flowing flowing water reflects a continuum of changing

environmental conditions from headwater streams to the river mouth. Headwater streams
depend on inputs of detrital material. As stream size increases, algae and rooted plants
become important energy sources, reflected in changing species composition of fish and
invertebrates life. Large rivers depend on fine particulate matter and dissolved organic matter
as sources of energy and nutrients. Life there is dominated by filter feeders and bottom-
feeding fish. Interrupting the downstream continuum of rivers are dams that impound water
and regulate the flow, completely changing the character of affected streams and rivers.
Dams hold back sediments from floodplains and riparian habitats and allow build-up of
sediments that normally would have been deposited on the floodplains and riparian habitats,
increase and decrease the intensity and volume of flow, and affect fish and invertebrate
populations

Self-Help: You can also refer to the sources below to help you further
understand the lesson:
Molles, M.C.Jr.(2016).Ecology Concepts and Applications.8th ed.Mcgraw-Hill International

Molles, Manuel C. Jr. (2019). Ecology. Concepts and Applications.8th edition

Smith,Thomas M. and Smith Robert Leo (2004).Elements of Ecology.5th ed.

Let’s check

A. LECTURE ACTIVITY

Activity1. One unique feature of a lake is its vertical and horizontal stratification. Your task
is to describe each layers or zones.
1. Littoral zone
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_____________________________________________________________________

2. Limnetic zone
_____________________________________________________________________
_____________________________________________________________________

3. Epilimnion
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_____________________________________________________________________

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

4. Metalimnion
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_____________________________________________________________________

5. Hypolimnion
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_____________________________________________________________________

Activity 2. Reflection

Your task in this activity is to research the current status of Philippine freshwater
resources such as rivers and lakes. Discuss the ecological issues affecting our freshwater
ecosystem. In addition, discuss also the pros and cons of Philippine Govt. Programs that are
currently implemented in addressing problems that you cited.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

Let’s analyze

Activity 1. As an ecologist, you should be able to describe the basic characteristics of

freshwater ecosystems such as rivers and lakes. Hence, I want you to explain your answers.

1. What physical characteristics are unique to flowing-water ecosystems?

_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

2. What is meant by river continuum?

_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

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 College of Arts and Sciences Education
BS Biology
renelee_subsuban@umindanao.edu.ph
(082) 300 - 5456 Local 118

3. What conditions distinguish the benthic zone from the other strata, and what is its role
in the lake ecosystem?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________

In a Nutshell

In this chapter, you were introduced to basic concepts and principles related to
Ecosystem Ecology (Freshwater ecosystem). I want you to cite the limiting factors that can
affect the biota of freshwater ecosystems. I will provide a sample then you continue the rest.

1. water temperature 4.

2. 5.

3. 6.

B.) LABORATORY ACTIVITY

 Perform Expt. 5. Refer to Ecology Laboratory Manual

 Further instructions regarding the procedures in relation to the conduct of
this experiment will be posted through LMS. Check it out!

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