Download Basic Ecology Chapter 1

Advanced Biology: Bahe & Deken
Basic Ecology
Chapter 1
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Advanced Biology: Bahe & Deken
1.1 - What is Ecology?
Think back to your experiences at Drey
Land. Think back especially to your
experiences at Bio Drey Land. What do you
remember? Do you remember all the work
you did? What was the point of all this
work? Do you remember the study of
Sinking Creek? What was the point of this
study? What was the point of the forest
study? The point was for you to learn about
the interactions between organisms and their
environment. Ecology is the study of how
living things interact with one another and
with their nonliving environment. As we
will find this semester, ecology is a critically
important field of biology, with implications
for all forms of life on Earth.
The interactions between living organisms
and the nonliving environment are two-way:
1) organisms are affected by their
environment, and 2) an organism’s very
presence and activities will change the
environment. As an example, plants extract
carbon dioxide from the air and emit oxygen
in the process of making food for
themselves (and in turn for organisms that
eat them). Remember photosynthesis:
6CO2 + 6H20
C6H12O6 + 6O2
Ecologist study environmental interactions
at several different levels (from a very
narrow perspective to a very broad
perspective). They may study at the
organism level, population level,
community level, or ecosystem level. At
the organism level an ecologist would
examine how one kind of organism interacts
with the environment. At the population
level an ecologist would examine how a
group of the same species interacts with the
environment. At the community level an
ecologist would examine how groups of
different species living in the same area
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interact with the environment. At the
ecosystem level an ecologist would examine
both the living and nonliving factors in a
certain area.
The biotic components of an ecosystem
include all of the living things making up a
community. The abiotic components
include all of the nonliving things in that
environment.
Questions at the organism level might
include: How does an organism meet the
challenges posed by its environment? How
does the physiology of the organism meet
these challenges? How does its behavior
meet these challenges?
Questions at the population level might
include: What challenges limit species
number in a certain population? How do
members of the same species interact with
one another?
Questions at the community level might
include: How do members of different
species interact? What are the predator and
prey relationships? Do groups of organisms
benefit one another? Do they harm one
another?
Questions at the ecosystem level might
include: How are chemicals cycled? How
does energy flow in an environment? How
do abiotic factors affect biotic factors? And
vice versa?
Ecologists studying at any of these levels
use the scientific process: posing
hypotheses and using observations and
experiments to test these hypotheses.
Ecologist may perform experiments in the
controlled environment of a laboratory or in
the field.
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What is a species?
Organisms can be classified into species, or
groups of organisms that resemble one
another in appearance, behavior, chemistry,
and genetic makeup. Some species
reproduce asexually. Unicellular organisms,
such as bacteria or amoeba, reproduce by
dividing into two cells identical to one
another as well as to the original parental
cell.
live on the soil and within the first meter or
two. The thin layer from the lower
atmosphere to the bottom of the oceans
makes up the biosphere. Other than the
need for the sun for warmth and for
photosynthesis, the biosphere is selfcontained, or closed. Energy can enter the
system but matter cannot (except for the
occasional meteorite).
Most organisms reproduced sexually,
producing offspring by combining gametes,
sperm and egg, from two separate parents.
Each offspring will be a combination of
characteristics from each parent and thus
different from each parent and from any
siblings (except for identical twins). This
variation in the offspring increases the
likelihood of species survival in the face of
environmental change.
Organisms that reproduce sexually are
classified as members of the same species if,
under natural conditions, they can breed
with one another and if they can produce
live, fertile offspring.
1.2 – The Biosphere – Home of Life
“On that small blue-and-white planet below
is everything that means anything to you.
National boundaries and human artifacts no
longer seem real. Only the biosphere, whole
and home of life.” Apollo astronaut Rusty
Schweickart.
The biosphere is the sum of all the
ecosystems on Earth. It includes part of the
atmosphere called the troposphere, all of
the water called the hydrosphere, and all of
the soil that contains life called the
lithosphere. Organisms live in the lower
part of the atmosphere as well as in almost
all the bodies of water on earth. Organisms
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If you look at the stylized depiction of the
Earth above you will notice its patchiness.
On the global scale you notice the different
continents and islands. On the regional
scale you would notice the deserts, forests,
grasslands, streams, lakes, etc. Even on a
local scale you would notice that forests are
a mixture of dense trees, small lakes,
meandering streams, and open meadows.
There is patchiness even on a smaller scale.
For example, you would find that each
stream has different habitats (specific
environments in which organisms live).
Each habitat has characteristic abiotic
factors that determine what kinds of
organisms will inhabit that environment –
water depth, temperature, dissolved oxygen,
pH, etc.
The merging of two ecosystems in a
transitional zone is called an ecotone.
Ecotones contain a mixture of species from
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adjacent ecosystems and often species not
found in either of the bordering ecosystems.
1.3 – Major Biomes of the Biosphere
A biome is a large geographic terrestrial
area with a characteristic climate and
specific life forms, especially vegetation that
is adapted to the climate. You are
undoubtedly familiar with some biomes.
The desert biome has very low rainfall and
often very warm temperatures. Other
examples of biomes are tropical rain forests,
grasslands, taigas (TEYE guh), and
deciduous forests. Each biome also has a
characteristic set of plants and animals.
Coniferous trees, pines, cedars, and spruces
with moose, wolves, weasels, and black bear
residing among the trees dominate the taiga
biome. Biomes are not restricted to land,
although watery regions are called aquatic
life zones instead. The open-ocean, coral
reefs, estuaries, and freshwater lakes are
aquatic life zones.
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The distribution of the biomes mainly
depends on two climatic characteristics,
annual rainfall and temperature variations.
The same biome can occur in two different
geographic locations (different continents) if
the climatic characteristics are very similar.
For example, deserts occur in North and
South America, in Africa, in Asia, and in
Australia. Biomes are characterized by the
type of communities that live there not by
specific populations. For example, the
groups of species living in the Sahara desert
in Africa and in the North American deserts
are different but each species is adapted
similarly to living in such a dry and warm
environment. Separated biomes may look
alike because of convergence, the evolution
of similar traits that evolved independently
in similar environments (we will discuss
convergence more when we study
evolution).
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Name:
Questions
1. An ecologist monitoring the number of
great apes in a wildlife refuge over a
five-year period is studying ecology at
which level?
a. Individual
b. Population
c. Community
d. Ecosystem
2. Which of the following is the most
complex?
a. community
b. individual
c. species
d. ecosystem
e. population
6. Is the following statement correct? Why
or why not?
A male horse and female donkey produce
sterile offspring called a hinny. Because a
horse and a donkey can successfully mate
they are the same species.
7. What is a habitat?
3. Which of the following is not an abiotic
factor that shapes ecosystems?
a. soil minerals
b. predators
c. fire
d. rainfall
e. storms
4. Which of the following shows how biotic
environmental factors can affect an
organism?
a. Maple trees will not grow in
waterlogged soil.
b. Some shrubs grow only where forest
fires scorch their seeds.
c. Trout will not live in shallow, warm
water.
d. Monarch butterflies live only where
there are milkweed plants for food.
5. Biomes depend most on
a. the plants and animals that live there.
b. continental location.
c. annual rainfall and temperature
variations.
d. solar energy and wind.
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8. What kinds of organisms live in an
ecotone?
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1.4 Biodiversity
To develop a meaningful understanding of
life on Earth, we need to know more about
species than their population size, such as
the composition of species on Earth. In its
simplest meaning biodiversity (or biological
diversity) is the variety of life on Earth.
Commonly biodiversity describes the
number of species among various groups of
organisms. It has been estimated that there
may be between 5 and 50 million species in
all; if so, many species are still to be found
and described. Ecologists describe
biodiversity on three levels:
1) Species diversity. All the
species in a particular area, including singlecelled bacteria and protists as well as the
species of the multicellular kingdoms
(plants, fungi, and animals).
2) Genetic diversity. The genetic
variation within members of a population,
both among geographically separate
populations and among individuals within
single populations.
3) Ecosystem diversity. The
different biological communities and their
associations with the abiotic environment.
Landscape diversity involves a group of
interacting ecosystems; for example, there
may be plains, mountains, and rivers. Of
course, biodiversity is
somewhat dependent on
landscape diversity.
By no means is
biodiversity evenly
distributed throughout the
biosphere. Biodiversity is
highest at the tropics, and
it declines toward each
pole on land, in
freshwater, and in the
ocean. In aquatic
ecosystems a higher
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degree of biodiversity is found in coral reefs
than any other part of the ocean. Some
regions of the world are called biodiversity
hotspots because they contain an unusually
large concentration of different species.
These hotspots contain about 44% of all
known higher plant species and 35% of all
terrestrial vertebrate species but cover less
than 1% of the Earth’s land area. The island
of Madagascar, the Cape region of South
Africa, Indonesia, the coast of California,
and the Great Barrier Reef of Australia are
all biodiversity hotspots.
Currently there are only about 1.75 million
species that have been described. As stated
above the undescribed species probably
number far more than those species that
have been described. Amazingly, around
20,000 new species are described each year.
Most birds, mammals, and temperate
flowers are well known, while in groups
such as insects, spiders, mites, nematodes,
and fungi, the number of described species
is still increasing at the rate of 1-2% per
year. A huge number of these species have
yet to be discovered, especially in the
tropical rain forests. Of these known
species, nearly 1,200 species in the United
States and 30,000 species worldwide are in
danger of extinction.
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Name:
Questions
Determine if the following statements is
describing (a) species diversity, (b) genetic
diversity, (c) ecosystem diversity, or (d)
landscape diversity. Put the most
appropriate letter next to each statement.
1. _______ Human hunters in the 1890s
reduced the population of northern elephant
seals in California to about 20 individuals.
Since then, this mammal has become a
protected species, and the population has
grown back to over 30,000 members.
However, in examining 24 genes in a
representative sample of seals, researchers
found no variation.
2. ________ In the 1830s Charles Darwin
observed the Galapagos Islands off the coast
of South America. He recorded the islands
were home to many unique organisms, most
of which were similar to, but different from,
the plants and animals of the nearest
mainland.
3. ________ North of the Missouri River
Missouri is characterized by rolling hills,
open, fertile plains, and well-watered prairie
land. Southwest of the river the land is
rough and hilly with deep, narrow valleys.
Southeast of the river the land consists of
alluvial plains.
Short Answer
4. Describe the uneven distribution of
diversity in the biosphere.
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5. What is the implication of uneven
distribution for conservation biologists?