People and the Earth Ecosystem:

A Modular Approach

BOBBY V. CABARLES
Special Lecturer

Department of Environmental Science

College of Science, UEP
SY: 2020-2021
Course code and Title
GEE People and the Earth Ecosystem—3 units (3 hours Lecture)

Overview
Have you ever hiked through a forest and noticed the incredible diversity of organisms
living together, from ferns to trees to mushrooms the size of dinner plates? Or taken a road trip
and watched the landscape change outside the window, shifting from oak forest to tall stands of
pine to grassy plains? If so, you’ve gotten a classic taste of ecology, the branch of biology that
examines how organisms interact with each other and with their physical environment.
Ecology isn't just about species-rich forests, pristine wilderness, or scenic vistas, though.
Have you, for instance, ever found cockroaches living under your bed, mold growing in your
shower, or even fungus creeping in between your toes? If so, then you’ve seen equally valid
examples of ecology in action.

Instruction to Students
Read and understand the content of this module. Work on various activities and develop a
sense of responsibility in accomplishing the tasks given. Learn how to Learn. And if you have
questions you may chat or email your teacher thru fb messenger or at
bobbycabarles37@gmail.com at a scheduled time. Also, an announced quiz via phone call will
be done to assess your understanding on the module given.

Requirements of the Course

1. Test/Quiz - 25%
2. Observation/Narrative Report/Project - 25%
3. Midterm and Final Examinations - 50%

Learning Outcomes
After studying this chapter, the learners are expected to:
1. Explain the most important objectives in the study of ecology.
2. Identify scientific procedures ecologists use to do in environmental investigation.
3. Understand linkages in the basic compositions of earth’s ecosystem.
4. Recall how organisms evolve from simple to its complex process of genetic variations.
5. Synthesize how species diversity arise.

Module 1
Introduction to Ecology
Every organism experiences complex relationships with other organisms of its species,
and organisms of different species. These complex interactions lead to different selective
pressures on organisms. The pressures together lead to natural selection, which causes
populations of species to evolve. Ecology is the study of these forces, what produces them, and
the complex relationships between organisms and each other, and organisms and their non-living
environment.
Scientist can view ecology through a variety of different lenses, from the microscopic
molecular level all the way to the planet as a whole. These different types of ecology will be
discussed further on. At every level of ecology, the focus is on the selective pressures that cause
evolutionary change. These pressures arise from a variety of different sources, and there are
numerous methods for observing and quantifying this data.
The field of ecology has a huge variety of sub-disciples. Although the types of ecology
below are divided by the level of organization being viewed, some ecologist specialize in
specific aspects of each field. Still other ecologists focus on the interactions between organisms
and the abiotic factors that affect their evolution, such as nutrients and toxins in the environment.

1.1 Why and How to Study Ecology

Importance of studying ecology
 Environmental
By studying ecology, the emphasis is put on how every organism needs
other for peaceful coexistence. Having no ideas on ecology will responsible
for degradation of land and environment, which is the living place of other
species leading to their destruction.
 Energy Conservation
The entire living organism needs energy such as nutrition, light, radiation
etc. So lack of ecological studies will be the cause for destruction of the Source:https//.Instantenergy.com
energy resources. Oil, coal, and natural gases are the non-renewable
sources which will destruct the ozone layer.
 Resource Allocation
All plants and animals have roles in the environment as they sharing limited natural resources
such as air, minerals, space. Lack of ecological studies may be the cause of deprivation and
looting of these natural resources.
 Eco-friendliness
It helps to appreciate living among the organisms; this will follow natural order of things.

1.2 Scientific Method

The study of environments generally begins with field observations. Field work often
starts with non-quantitative observations. A researcher may take a stroll through the forest or
snorkel a reef to look around. Once ecologists have an idea of the system, they can determine
what data they’re interested in collecting. It is never possible to measure everything all of the
time, so ecologists need to make decisions about the frequency of measurements and types of
measurements to take. Some data collection can be automated, through the use of sensors or
research post, such as the heights of trees in the forest. Other data collection methods, like
vegetation surveys or animal trapping, must be done in person. The data from field work helps
ecologists figure out the right questions to ask.

What are the three methods ecologists use to do?

 Experiments
Field data is a great first step to understanding an ecosystem, but there are always
questions that can’t be answered with the field surveys. In these cases, ecologists will
employ manipulative experiments with a control treatment to test hypotheses about
the way an ecosystem works. For example, a famous set of experiments by Prof.
Stephen Carpenter of the University of Wisconsin involved adding top predator fish
Source: ww.pinterest.com
to lakes to see if this would control primary production. The idea was based off of
observational data about how lakes changed after winter fish kills. Carpenter’s research
team found that more predator fish leads to: 1) less small fish, 2) more zooplankton and 3)
less phytoplankton. Called a trophic cascade, these experiments have led to improved
management of lakes across the world and other ecosystems like Yellowstone
National Park.
 Modeling
Modeling is an important tool that ecologists employ to study ecosystems once
they think they understand how the ecosystem of an environment works. A
model can take many forms, but it represents a specific hypothesis about the
mechanics of an ecosystem. The power of modeling is that a good model can
let researchers test a range of scenarios that would be too expensive or difficult Source:hptts//.2002 W.F Ruddiman

to do as experiments. Models can help ecologists make predictions about

things as varied as how changes to fisheries regulations will affect fisheries stocks or how
climate change will impact the ranges of disease carrying species like mosquitoes. Models
that predict range expansion of disease carrying mosquitoes can be used to inform doctors in
at-risk areas to be on the lookout for new diseases such as malaria that may not have
occurred there before.
 Synthesis
The most powerful research projects are ones that bring together field
observations, experiments and modeling. There are programs in place today
that are designed to create opportunities for synthesis of these different
research methods. For instance, the National Ecological Observatory Network
(NEON) is a new network of locations where a huge range of data will be
collected for 30 years following its completed construction. According to
information obtained March 2014 from the NEON website, construction has
Source: www.vabba.pw
been completed on 25 sites, and 27 sites are planned for construction in 2014.
At these sites there are also facilities for ecologists to perform experiments,
utilizing the data being collected. The experiments and observational data will be used to
build continent-scale models to predict how the environment will respond to threats like
invasive species and climate change.
1.3 The Effects of Scale
Within the discipline of ecology, researchers work at five broad levels, sometimes
discretely and sometimes with overlap: organism, population, community, ecosystem, and
biosphere.

Let's take a look at each scale.

Individual/Organism-Organismal ecologists study adaptations,
beneficial features arising by natural selection that allow organisms to
live in specific habitats. These adaptations can be morphological,
physiological, or behavioral.
Population -A population is a group of organisms of the same species
that live in the same area at the same time. Population ecologists
Source:www.pinterest.com
study the size, density, and structure of populations and how they
change over time.
Community-A biological community consists of all the populations of different species that live
in a given area. Community ecologists focus on interactions between populations and how these
interactions shape the community.
Ecosystem-An ecosystem consists of all the organisms in an area, the community, and the
abiotic factors that influence that community. Ecosystem ecologists often focus on flow of
energy and recycling of nutrients.
Biosphere- The biosphere is planet Earth, viewed as an ecological system. Ecologists working at
the biosphere level may study global patterns—for example, climate or species distribution—
interactions among ecosystems, and phenomena that affect the entire
globe, such as climate change.

A flow chart of three boxes explaining the hierarchy of living organisms.

WW
The top box contains a photograph of tall trees in a forest and is captioned,
“Organisms, populations, and communities: In this forest, each pine tree is
an organism. All of the pine trees living in the area make up a population.
All of the populations of different species in the area form a
Source:hptts//.Khanacademy.org
community. “The second box contains a photograph of a body of
water, behind which a stand of tall grasses is developing into more
dense vegetation and trees as distance from the water increases. The
photo is accompanied by the following text: “Ecosystems: This coastal ecosystem in the
southeastern United States consists of a community of living organisms plus their physical
environment. “The third box contains a drawing of planet Earth and is labeled, “The biosphere:
The biosphere consists of all the ecosystems on Earth, considered together. A flow chart of three
boxes explaining the hierarchy of living organisms. The five levels of ecology are listed above
from small to large. They build progressively—populations are made up of individuals;
communities are made up of populations; ecosystems are made up of a community plus its
environment; and so forth. Each level of organization has emergent properties, new properties
that are not present in the level's component parts but emerge from these parts' interactions and
relationships. The levels of ecological study offer different insights into how organisms interact
with each other and the environment. I like to think of these levels as magnifying glasses of
different strengths. If you really want to get what's going on in a particular ecological system,
you'll likely want to use more than one!

1.4 Evolutionary Ecology

If you have spent some time studying biology, then you have likely seen pictures of early
human species. It probably did not take you long to realize that we have changed rather
significantly over the years, however, do you know what caused those changes? Evolution is the
development of changes that can be passed genetically over the history of an organism.
These changes happen for a reason: when everything is going well for an organism, it has
no reason to change anything. However, when conditions are not so favorable anymore, an
organism may consider changing in order to have a better chance of surviving. Scientists study
these pressures when they study ecology, which is the study of the interactions between an
organism and its environment.
To fully understand ecology, you have to keep in mind that there are many different
aspects of an organism's environment. These include other organisms of the same species, other
species of organisms, and the nonliving parts of the environment. When we study how these
ecological factors cause changes in an organism throughout its history, we are studying
evolutionary ecology.

1.5 How Variation Originated

Genetic variation is a measure of the variation that exists in the genetic makeup of
individuals within population. The genetic variation of an entire species is often called genetic
diversity. Genetic variations are the differences in DNA segments or genes between individuals
and each variation of a gene is called an allele. For example, a population with many different
alleles at a single chromosome locus has a high amount of genetic variation. Genetic variation is
essential for natural selection because natural selection can only increase or decrease frequency
of alleles that already exist in the population.

Genetic variation is caused by:

 Mutation
Mutations are changes to an organism’s DNA and are an important
driver of diversity in populations. Species evolve because of the
accumulation of mutations that occur over time. The appearance of

Source: internationalbusinesstimes.org
new mutations is the most common way to introduce novel genotypic and phenotypic
variance. Some mutations are unfavorable or harmful and are quickly eliminated from the
population by natural selection. Others are beneficial and will spread through the population.
Whether or not a mutation is beneficial or harmful is determined by whether it helps an
organism survive to sexual maturity and reproduce. Some mutations have no effect on an
organism and can linger, unaffected by natural selection, in the genome while others can
have a dramatic effect on a gene and the resulting phenotype.
 Random mating between organisms
In random mattings involves the mating of individuals regardless of
any physical genetic or social preference. In other words the mating
between two organisms is not influenced by any environmental,
hereditary, social interactions, hence potential mates have an equal
chance of being selected.
Source: www.miami.edu
 Random fertilization
Refers to the fact that if two individuals mate, and each is capable of producing over eight
million potential gametes, the random chance of any one sperm and egg coming together is a
product of these two probabilities-some seventy trillion different combinations of
chromosomes in a potential offspring.
 Crossing over (or recombination) between chromatids of homologous chromosomes
during meiosis
Is the exchange of genetic material during sexual reproduction
between two homologous.
 Evolution and Adaptation to the Environment
Variation allows some individuals within a population to adapt to the
changing environment. Because natural selection acts directly only
on phenotypes, more genetic variation within a population usually Source; Chegg.com
enables more phenotypic variation. Some new alleles increase an
organism’s ability to survive and reproduce, which then ensures the survival of the allele in
the population. Other new alleles may be immediately detrimental (such as a malformed
oxygen-carrying protein) and organisms carrying these new mutations will die out. Neutral
alleles are neither selected for nor against and usually remain in the population. Genetic
variation is advantageous because it enables some individuals and, therefore, a population, to
survive despite a changing environment.

 Geographic Variation
Some species display geographic variation as well as variation within a
population. Geographic variation, or the distinctions in the genetic makeup
of different populations, often occurs when populations are geographically

Source; Dragongflyissueinevolution13.com
 separated by environmental barriers or when they are under selection pressures from a
different environment. One example of geographic variation are clines: graded changes in a
character down a geographic axis.

Sources of Genetic Variation

Gene duplication, mutation, or other processes can produce new genes and alleles and
increase genetic variation. New genetic variation can be created within generations in a
population, so a population with rapid reproduction rates will probably have high genetic
variation. However, existing genes can be arranged in new ways from chromosomal crossing
over and recombination in sexual reproduction. Overall, the main sources of genetic variation are
the formation of new alleles, the altering of gene number or position, rapid reproduction, and
sexual reproduction.
 Genetic Drift
Genetic drift is the change in allele frequencies of a
population due to random chance events, such as natural
disasters.

Source:www.pinterest.com

 The Bottleneck Effect

Genetic drift can also be magnified by natural events, such
as a natural disaster that kills a large portion of the
population at random. The bottleneck effect occurs when
only a few individuals survive and reduces variation in the
gene pool of a population. The genetic structure of the
survivors becomes the genetic structure of the entire
population, which may be very different from the pre-
disaster population. Source;https//study.com/

 The Founder Effect

Another scenario in which populations might experience a
strong influence of genetic drift is if some portion of the
population leaves to start a new population in a new location
or if a population gets divided by a physical barrier of some
kind. In this situation, it is improbable that those individuals
are representative of the entire population, which results in
the founder effect. The founder effect occurs when the genetic Source;Teacherspayteachers.gov
structure changes to match that of the new population’s
founding fathers and mothers.
 Drift and fixation
The Hardy–Weinberg principle states that within sufficiently large
populations, the allele frequencies remain constant from one

Source: Slideplayer.com
generation to the next unless the equilibrium is disturbed by migration, genetic mutation, or
selection. Because the random sampling can remove, but not replace, an allele, and because
random declines or increases in allele frequency influence expected allele distributions for
the next generation, genetic drift drives a population towards genetic uniformity over time.
When an allele reaches a frequency of 1 (100%) it is said to be “fixed” in the population and
when an allele reaches a frequency of 0 (0%) it is lost. Once an allele becomes fixed, genetic
drift for that allele comes to a halt, and the allele frequency cannot change unless a new allele
is introduced in the population via mutation or gene flow. Thus even while genetic drift is a
random, directionless process, it acts to eliminate genetic variation over time.
 Gene Flow and Mutation
An important evolutionary force is gene flow: the flow of alleles in and out of a population
due to the migration of individuals or gametes. While some populations are fairly stable,
others experience more movement and fluctuation. Many plants, for example, send their
pollen by wind, insects, or birds to pollinate other populations of the same species some
distance away. Even a population that may initially appear to be stable, such as a pride of
lions, can receive new genetic variation as developing males leave their mothers to form new
prides with genetically-unrelated females. This variable flow of individuals in and out of the
group not only changes the gene structure of the population, but can also introduce new
genetic variation to populations in different geological
locations and habitats.
A population’s genetic variation changes as individuals
migrate into or out of a population and when mutations
introduce new alleles.

Source:m.wikepedia.com

 Nonrandom Mating and Environmental Variance

Population structure can be altered by nonrandom mating (the
preference of certain individuals for mates) as well as the
environment.Genes are not the only players involved in
determining population variation. Phenotypes are also
influenced by other factors, such as the environment. A
beachgoer is likely to have darker skin than a city dweller, for
example, due to regular exposure to the sun, an environmental
factor. Some major characteristics, such as gender, are Source:weekly.com
determined by the environment for some species. For example,
some turtles and other reptiles have temperature-dependent sex determination (TSD). TSD
means that individuals develop into males if their eggs are incubated within a certain
temperature range, or females at a different temperature range. TT
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phylogenetics

2. biologydictionary.net>ecology (Retrieved by BD editors 2017)

3. Mahantry, S. (20017) Research and Reviews: Journal of Ecology and

Environmental Sciences
4. Steele, J. (2015) What are the three Ecologist Use to Study the Environment?

5. The Evolution of Population (n.d.) Retrieve 2020 from

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