Download Chapter 19 Introduction to Ecology

Chapter 19 Introduction to Ecology
Ecology – the study of the interactions between organisms and the living and
nonliving parts of their environments.
Today’s Issues
- The study of ecological information has been around for a very long
time.
- Over the past few decades, humans have changed the environment on
a greater scale than ever before in history.
1. The Exploding Human Population
- The current world population is: 6,592,491,071
- The increasing population leads to overcrowding; we need more food,
more energy, more space to live, and more space for disposal of
waste.
2. The 6th Mass extinction
- As the human population increased, many other species have declined
in numbers or become extinct.
o All due to habitat destruction, over hunting, and introduction to
diseases and predators.
- There is fossil evidence about 5 previous mass extinctions; we are
causing the 6th.
o This extinction is happening faster than any of the previous
extinctions.
o Scientists estimate that about 1/5 of the species in the world
may disappear in the next century.
3. The Thinning Ozone layer
- In 1985, British scientists discovered a hold in the ozone layer over
Antarctica.
- In 1992, there was a treaty formed that banned the use of CFCs and
other ozone-destroying chemicals.
o It’s important to note that normal ozone lets through about 1%
of the sun’s UV radiation. Think about how many sunburns are
caused or how much skin cancer is caused just because of that
1%.
4. Climate Changes
- The Greenhouse Effect – the mechanism by which greenhouse gases,
such as carbon dioxide and water vapor, trap heat in the upper
atmosphere and deflect it back to Earth, thereby insulating the Earth
and overheating it.
- The burning of fossil fuels (coal, oil, and natural gas) has caused the
concentration of CO2 to increase 25% in the last 100 years.
- Since 1860, the average global temperature has risen about 0.6oC
(1oF).
- It is estimated that by the year 2100, the average global temperature
will rise about 1.5 – 4.5 oC (3-8oF)
o This increase in temperature will be sure to cause rising sea
levels due to the melting of the polar ice caps.
Levels of Organization
- Scientists recognize a hierarchy of different levels of organization
within organisms.
- Each level has unique properties that result from interactions among
its components.
The Biosphere
- The most inclusive level.
- It is the thin volume of Earth and its atmosphere that supports life.
o It’s about 20km thick and extends about 8-10km above the
Earth’s surface to the deep parts of the oceans.
Ecosystems
- All the organisms and the nonliving parts of the environment found
within a particular place.
o Example: a pond
Communities, Populations, and Organisms
- A community is all the interacting organisms living in an area.
- A population includes all of the members of a single species that live
in one place.
- The simplest level of organization is that of the organism.
A key theme in Ecology
- It is important to remember that when you study Ecology, no
organism is isolated. The theme of interconnectedness of all
organisms is central to the study of Ecology.
- Each ecosystem is a network in which organisms are linked to other
organisms and to the nonliving parts of the environment.
- Any disturbance or change in an ecosystem can spread through the
network of interactions and affect the ecosystem in widespread and
often unexpected ways.
Ecological Models
- Ecosystems are extremely complex and difficult to study. One way
Ecologists deal with this complexity is to use models.
- A model may be visual, verbal, or mathematical. They are often
based on predictions.
- A model can be used to test a hypothesis.
o For example, predicting future behavior of the ecosystem.
- Models are often used to help plan and evaluate solutions to
environmental problems.
Section 19.2 Ecology of Organisms
- Answers to complex questions about ecology involve looking at the
organism’s evolutionary history, its tolerances and requirements, and
the history and conditions of its habitat (where it lives).
Biotic and Abiotic Factors
- Biotic factors are the living components of the environment and
include all of the living things that affect the organism.
- Abiotic factors are the physical and chemical characteristics of the
environment.
o Temperature, humidity, pH, salinity, oxygen concentration, etc.
- These factors are not independent of one another. Organisms change
their environments and are influences by it.
The changing environment
- Abiotic factors are not constant. They vary from place to place and
over time.
o Example, think about how quickly temperature can change and
how different the temperatures are across the country and
world.
Responses to a changing environment
- Organisms are able to survive within a wide range of environmental
conditions.
- Ecologists measure how well an organism can survive at extremes by
measuring how well it performs its functions at those extremes.
o A graph of performance can then be constructed. This graph is
called the organism’s tolerance curve.
o An organism cannot live in areas out its tolerance limits.
Acclimation
- Some organisms can adjust their tolerance to abiotic factors through
the process of acclimation.
o For example, if you spend a few weeks at high altitude, your
body will “acclimate’ (adjust) to the reduced oxygen level.
Over time, your body will start producing more RBCs to
increase the amount of oxygen in your body.
Control of Internal conditions
- There are 2 ways for organisms to deal with some changes to their
environments: they can become a conformer, or a regulator.
o A conformer does not change their internal environment, but
rather they change their external environment.
o A regulator is an organism that uses energy to control some of
their internal conditions.
 They’ll try and keep their internal conditions within
optimal range over a wide variety of environmental
conditions.
Escape from unsuitable conditions
- Some species can survive unsuitable conditions by escaping from the
temporarily.
o For example, some organisms become dormant.
 They enter a state of reduced activity during periods of
unfavorable conditions.
- Another escape strategy is to migrate.
o To move to a more favorable environment.
Resources
- Whether a species can survive in a particular habitat depends on the
suitability of environmental conditions and also the availability of
resources.
o Resources – the energy and materials the species needs to
survive.
The Niche
- A species’ niche is its way of life, or the role the species plays in its
environment.
- It includes a wide range of conditions that the species can tolerate, the
methods by which it obtains needed resources, the number of
offspring it has, its time of reproduction, and all of its other
interactions with its environment.
- The fundamental niche is the range of conditions that a species can
potentially tolerate and the range of resources it can potentially use.
- The realized niche of a species is the range of resources it actually
uses.
Niche Differences
- A species’ niche can change within a single generation.
o Example – caterpillar to butterfly.
- Generalists are species with broad niches; they can tolerate a range of
conditions and use a variety of resources.
- Species that have narrow niches are called specialists.