An Introduction to Ecology and
the Biosphere
Chapter 50
Ecology and Evolutionary Biology
• Darwin’s extensive observations of the distribution of organisms and
their adaptation to specific environments led him to propose that
environmental factors interacting with variation within populations
could cause evolutionary change.
• Events that occur in the framework of ecological time (minutes,
months, and years) translate into effects over the longer scale of
evolutionary time (decades, centuries, millennia, and so on).
- Example: Hawks feed on field mice have an immediate impact on
the prey population by killing individuals, and reducing population
size. (Ecological effect) This also alters the gene pool. (Evolutionary
effect)
Organisms and the Environment
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The environment of any organism includes:
Abiotic- Nonliving components; chemical and physical factors such as temperature,
light water and nutrients.
Biotic- Living components; all the organisms (biota) that are part of the
environment.
- Other organisms may compete for resources, prey upon others, parasitize others,
provide food, or change the physical and chemical environment.
Example: Studies suggest that an abiotic factor, the amount and variability of
precipitation, influences the distribution of red kangaroos in Australia.
- Are the controls on red kangaroo distribution only abiotic? Multiple factors could
affect patterns of distribution and abundance; for example climate could be
indirectly affecting red kangaroo distribution through biotic factors such as
pathogens.
Subfields of Ecology
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Organismal ecology - concerns how an organism’s structure, physiology, and behavior meet the
challenges posed by the environment.
- May be subdivided into the disciplines of physiological, evolutionary, and behavioral ecology.
Population ecology - concentrates mainly on factors that affect how many individuals of a
particular species live in an area.
Community ecology - (an assemblage of populations of many different species) deals with the
whole array of interacting species in a community.
-Focuses on how interactions such as predation, competition, and disease, as well as abiotic factors
such as disturbance, affect a community structure and organization.
Ecosystem ecology - (consists of all abiotic factors in addition to the entire community of species
that exist in a certain area) the emphasis is on energy flow and chemical cycling among the various
biotic and abiotic components.
Landscape ecology - deals with arrays of ecosystems and how they are arranged in a geographic
region.
- Consists of a mosaic of different types of “patches”, referred to as patchiness.
- Focuses on the factors controlling exchanges of energy, materials, and organisms among the
ecosystem patches making up landscape or seascape.
Biosphere – the sum of all the planet’s ecosystems (the global ecosystem).
- This broadest area of ecology includes the entire portion of Earth inhabited by life.
Ecology and Environmental Issues
• To address environmental problems, we need to understand often
complicated and delicate relationships between organisms and the
environment. The science of ecology provides that understanding.
• Most of societies awareness of environmental issues began in1962 with
Rachel Caron’s Silent Spring. (Spread awareness of the harms of DDT)
• Many influential ecologists recognize a responsibility to educate legislators
and the general public about decisions that affect the environment.
• Although our ecological information is always incomplete, we must make
decisions about environmental issues. Given what we do know about the
interconnectedness of the biosphere, it is wise to follow:
The precautionary principle- “An ounce of prevention is worth a pound of
cure”.
---->Briefing on DDT<---• DDT is an extremely strong and lethal pesticide. In the past it
was used greatly during WW2 to stop mosquitoes from
spreading malaria. It was a cheap pesticide that was believed
to have a low toxicity to mammals. Then problems /of DDT
began to appear. DDT entered the food chain and got stored
in the fatty tissues of the animals. In 1972 many people
acknowledged and realized the long-lasting effects of DDy and
it was banned.
Section 50.2 - Interactions between organisms and the environment
limit the distribution of species.
The study of the distribution of organisms past and present is called biogeography. There are several factors
that influence (limit) an organism’s distribution.
1) dispersal: the movement of individuals away from high population or area of origin.
Dispersal can be seen when organisms move to areas where they didn’t exist previously. This is called
natural range expansion. Another way in which dispersal can be seen is through species transplants.
Species that are moved to a new area must not only survive but reproduce.
2) behavior: One such behavior that can limit distribution is habitat selection. Animals and
plants both have habitat selection behavior. An example is female insects that only deposit eggs in response
to certain stimuli.
3) biotic factors: Do other species limit distribution? Other species can limit the distribution of
a certain species through predation, parasitism, disease, or competition, or a species can be limited if another
species which they depend on is missing from the new habitat.
4) abiotic factors: temperature, water, sunlight, wind, and rocks and soil. Temperature affects
biological processes and internal temperatures. Water affects distribution in that organisms depend on
either salt or freshwater. Sunlight drives nearly all ecosystems because of the energy it provides. It is also
very important in aquatic ecosystems and to organisms that are sensitive to photoperiod (daytime and
nighttime). Wind effects temperature (increase heat loss) and water loss (increase rate of evaporative
cooling). Rocks and soil can affect water chemistry.
5) climate: Climate affects the distribution of species in that it varies in particular areas. For
example, a species that needs to live in waters of a fairly warm temperature can’t be swimming in the arctic
where the waters are very cold. Furthermore, seasonality affects distribution. For instance, birds fly south
or north depending on the season.
How DDT Affects the Distribution of
Organisms
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DDT is a pesticide that can be lethal in certain quantities. It could affect organisms
by limiting and perhaps even allowing distribution. The simplest way DDT can
limit the distribution of organisms is by killing a large portion of a species at its
original habitat. Obviously, if the animal is dead from DDT, it cannot move and
disperse itself. In addition, if a species was relocating to a new habitat that had
been infected with DDT, it would be killed at the new habitat, perhaps before it had
any chance of reproducing.
It was mentioned that biotic factors such as other species limit distribution. If
at a new habitat DDT had killed a certain predator, then a new species that would
have been prey at the new habitat can move to this new location. Instead of being
killed by the predator and being removed from the new habitat, the species can
prosper there. Also, if a species’ habitat was sprayed with DDT, and the species
was able to detect that their habitat had been infected, the species could move to a
new habitat to avoid death.
Distribution is effected by population
increase.
• Distribution is effected by population increase because as population
increases, animals of the same species will begin to cause too much
competition for resources in an area. This causes some animals to explore
new regions in search of a suitable place to live and reproduce that is not
as overpopulated.
• Population increase can also aid small populations in becoming more
established. This causes the species to become more distributed among a
certain area. This can also create more prey or predation (depending on
the species of increase) and cause predators or prey to distribute into new
areas; such as predators moving into the area to prey upon the species of
increase.
Abiotic and biotic factors influence the
structure and dynamics of aquatic
biomes
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Biotic and abiotic factors greatly influence the distribution of organisms of Earth.
The combination of these factors make up the Earth’s many biomes.
Biomes are any of the world’s major ecosystems that was classified according to
the predominant vegetation and characterized by adaptations of organisms to that
particular environment.
Aquatic biomes account for the largest portion of the biosphere in terms of area.
Two types: Freshwater Biomes
Marine Biomes
The two are distinguished by their physical and chemical differences.
EX: Freshwater Biomes have salt concentrations less then 1% whereas Marine
Biomes generally average 3%.
• Marine Biomes
- The oceans cover about 75% of the Earth’s surface
- The evaporation of water from the oceans provides most of the plants
rainfall
- The ocean temperatures have a huge effect on world climate and wind
patterns
Marine algae and photosynthetic bacteria supply a big portion of the
world’s oxygen and consume huge amounts of carbon dioxide.
• Freshwater Biomes
- The biomes are closely connected to the soils and other components of
the of the terrestrial biomes through which they pass or are situated in.
- The characteristics of the biomes are decided by the patterns and speed
of water flow and climate in which the biome is in.
• Photic Zone
-area where there is sufficient light for photosynthesis and where
phytoplankton, zooplankton, and many fish species live
• Aphotic Zone
-area where little light penetrates and has very little life except for
microorganisms and luminescent fishes
• Benthic Zone
-area at the bottom of all aquatic biomes where communities of
organisms called benthos live and consume detritus which rains
down from the productive surface of the photic zone
• Abyssal Zone
-area that is the deepest region of the ocean floor
• Thermal energy from sunlight warms the surface waters to where
ever the sunlight can reach, however the rest of the waters remain
cold. A thermocline, which is a narrow stratum of rapid
temperature change, separates the warm upper layer from the cold
deeper waters.
Details of Effect DDT on Abiotic and
Biotic Factors in Aquatic Biomes
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DDT can have a horrible effect on abiotic and biotic factors that
influence the components of aquatic biomes. Aquatic biomes are all
interconnecting because of evaporation, rainfall, currents, etc.
Water that is in Mississippi can go through the water cycle and end
up in India. This means that if there is DDT in the water supply, it
can affect not only the area in which the water is in, but the areas in
which the water may cycle too. All of Earth’s water supply could
sooner or later be affected by DDT. Even if it’s just used in certain
areas, water flows can take the water else where, slowly but surely
contaminated the fish and animals of the area.
DDT mainly effects biotic factors since all living things take in
nutrients. All organisms need water to survive, so when water is
contaminated, other organisms suffer because they're ingesting the
poison into their bodies. Even if the organisms don't directly use the
contaminated water, they will still end up having DDT coursing thru
their veins because of the food chain.
Population increase effects Biotic
Factors, and the Ozone Hole effects
Abiotic Factors.
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Other species limit the distribution of a species. A population increase can
cause an increase in negative interactions between species such as predation,
parasitism, disease, or competition. An increase in population of a certain
species may cause another species to have an inability to survive and
reproduce.
This inability may also occur in the absence of another species on which a
transplanted species depends. If the population of a species is too great, and
limits the population of another required species or over hunts its prey, both
species affected will decrease, even if not at the same time.
The hole in the ozone layer affects sunlight, an abiotic factor. This hole causes
greater amounts of sunlight to pass through the atmosphere at stronger
levels. Sunlight provides energy that drives nearly all ecosystems. The intensity
and quality of sunlight limits the distribution of photosynthetic organisms. The
hole in the ozone layer affects the intensity and quality of sunlight that
photosynthetic organisms receive, which can be harmful to them. Many of
these organisms may suffer population increases, and eventually, entire
ecosystems may be affected.
TERRESTRIAL BIOMES
• Terrestrial biomes are named for their physical or climatic
factors and the predominant vegetation. Climographs are
used to plot the temperature and precipitation of biomes
which gives us evidence of the distribution of biomes. These
biomes are characterized from the microorganisms, fungi and
the animals. Typical features of terrestrial biomes may include
their vertical stratification and the way the biomes grade into
each other, also called as econtone.
• Examples of terrestrial biomes include: desert, topical forest,
tundra, and savanna
Details of effect on DDT on Terrestrial
Biomes
• The pesticide DDT can have a tremendous and negative effect onto
Terrestrial biomes. If DDT enters the soil of terrestrial biomes it can effect
the species living there because it enters the food chain and in the fatty
tissues of animals. Many of the organisms health will vary leading to many
illnesses and deaths. DDT is passed from one organism to another. If an
animal contains DDT and is used as prey the predator will then contain the
pesticide, and so on and so forth. Thus leading to a chain. (Example of this
is on birds.) The population in the biomes will suffer as well as one of the
factors that distinguishes one terrestrial biome to another. DDT can also
effect Terrestrial biomes by effecting the plants. It can destroy the plant
habitat which would lead to many long-lasting effects. One effect would
be on the vertical stratification which varies on the shapes and sizing of
plants.( a very important feature of the terrestrial biomes) Stratification
also serves as a habitat for animals. If it is effected by DDT it will also
effect the animals habitats. In addition food would become more scarce,
and the food living will be also contaminated from DDT. The animals eating
that plant will take in the pesticide and thus the pesticide will be entered
in the food chain.
Global Warming effects climate and
terrestrial biomes.
• Temperature and rainfall are important to the distribution of biomes.
When global warming interferes with the overall temperature of the
earth, terrestrial biomes are directly effected. As temperature increases
the variety of terrestrial biomes becomes more limited due to a smaller
range of weather conditions. Terrestrial biomes that can tolerate warmer
climates, such as deserts and tropical forests, will increase. Terrestrial
biomes that exist in cooler climates, such as tundra and polar ice, will
decrease over time.
• Regions where biomes overlap may be affected as well, and cause one
biome, that flourishes in a warmer climate, to dominate the area.
• Currently, scientists have found that global warming has caused the polar
ice caps to begin melting.