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BIO Module 6 Overview
Ecosystems and Ecology
This module will continue the examination of fundamental concepts related to ecology. It
will introduce the complex phenomena of interactions between organisms and their habitats,
as well as the delicate interactions between communities of organisms. It will explain why
changing one part of a community can lead to unexpected consequences. This module will
also examine the concept of populations and their growth curves. This material is relevant
to the question of a population's "carrying capacity," and, in turn, the Malthusian theory of
overpopulation. Finally, you will delve into the fascinating issues surrounding instinctive
and learned behavior among animals.
Learning Objectives
Upon completion of this module, you should be able to:
9A Describe the flow of atoms through the carbon, nitrogen, phosphorus, and
hydrologic cycles.
9B Identify biotic and abiotic environmental factors.
9C State the importance of bacteria in nutrient cycles.
9D Examine the role of decomposers.
9E Explain how energy is related to ecosystems.
9F Determine why plants are called producers.
9G Identify the trophic levels occupied by herbivores and carnivores, and why they
are called consumers.
9H State the benefits and shortcomings of using each of the following: pyramid of
numbers, pyramid of biomass, and pyramid of energy.
9I Describe the kinds of ecosystems that have been converted to agriculture.
9J Explain why people in poor countries eat mostly plant material.
9K Differentiate among predation, mutualism, competition, parasitism, and
commensalism.
9L Distinguish between niche and habitat.
9M Relate extinctions to human activities.
9N Describe an organism’s niche, habitat, and community.
9O Determine the effect humans have had on natural climax ecosystems.
9P List typical abiotic and biotic characteristics of different biomes.
9Q Explain why persistent organic chemicals reach higher levels in carnivores than in
herbivores.
9R Describe the effect of temperature and rainfall to the kind of biome that
develops.
9S State why some plants and animals are found only in certain parts of the world.
9T Explain the concept of a climax community.
9U Identify the factors that ultimately limit population size.
9V State why the human population must have an upper limit.
9W Specify the importance of birthrates and death rates to population growth.
9X Define a population and identify key components that affect population growth.
Module 6 Reading Assignment
Enger, E. D., Ross, F. C., & Bailey, D. B. (2012). Concepts in biology (14th ed.). New York:
McGraw-Hill. Chapters 15, 16, and 17.
Optional Reading Assignment:
Chapter 18, Evolutionary and Ecological Aspects of Behavior.
Ecosystems and Ecology
Abiotic factors are characterized as nonliving. Weather, including temperature and
precipitation, make up a large part of the abiotic factors as well as things in the natural
environment such as mountains, oceans, and deserts. Of course, that is a large list of
nonliving factors that living things come into contact with constantly such as sunlight and
wind. Biotic factors are characterized as living things, animals, plants, fungi, and bacteria,
which in one way or another affect the ecosystem. Each of these living things also needs
abiotic factors in order to survive. Living things could not survive without water and
oxygen. Please watch the What's the difference between biotic and abiotic factors
video.
Producers are organisms that harvest sunlight and harvest it to make molecules with the
help of photosynthesis. Producers use sunlight energy by converting it into energy that can
be used in the format of organic molecules and then stored for later use. Plants using
photosynthesis, or producers, help jump-start the flow of energy throughout the ecosystem.
All organisms other than plants, or producers, are considered to be consumers. All living
organisms need organic molecules for their energy. Consumers include herbivores,
carnivores, and omnivores.
Decomposers are able to break down nonliving organic materials into inorganic molecules.
Decomposers allow for producers to reuse them. This is a very primitive way of recycling,
but it also keeps the ecosystem moving by recycling all the inorganic molecules back to the
producers where they can again create energy.
An organism’s niche, habitat, and community are all very much intertwined. The niche of
an organism is the part it fills within a community or its job, the food it eats, where it
resides, and its schedule. It is nearly impossible to completely describe an organism’s niche
in full because both biotic and abiotic environments impact the organism; therefore, the list
would be too detailed. Plus, each organism is held accountable within the community to be
upheld.
An organism’s habitat is where the organism lives. The borders of a habitat are very easily
blurred because it is difficult to know where one habitat ends and another habitat begins.
The climate, or temperature and rainfall, plays an important role in defining the type of
habitat. Having a set climate, whether it is a beach, desert, flat land, glacier, or
mountainous, helps differentiate among the habitats.
An organism’s community is made up of different populations all living within one habitat.
All of the organisms interact with one another in some shape or form. Within a community
lies a habitat and within that habitat lies individual niches.
A population within the terms of biology is a cluster of organisms living in the same space
that also belong to the same species. Within each population, there is something called age
distribution. The population is broken down into three categories: juveniles, reproductive
adults, and post-reproductive adults. The amounts in each of these categories vary widely
from population to population, especially from populations whose life spans are a few weeks
long compared to humans who span several decades.
All species have what are called limiting factors that help control the population of the
species. Limiting factors include the availability of raw materials, the availability of energy,
the accumulation of waste, and the interactions of others or other species. Each of these
limiting factors could mean different things for different populations.
For humans, the availability of raw materials is very important for the continual growth and
the ability to sustain life. The availability of clean water, materials to build shelter, and
harvesting energy and food are at the core of what we need in order to survive; therefore,
these are all big, limiting factors for the human population. The availability of energy,
again, is an important factor for the human population—not just in the sense of harnessing
energy to fuel our homes and economy, but in the sunlight that triggers the production of
our food supply. The accumulation of waste has the potential to cause infection and illness
from the growth of bacteria. For us as humans, the waste also affects our environment on
a large level from the air we breathe to the water we drink. As for the interaction with
others, it can be a double-edged sword. It can cause conflict and war, but it can also help
us to provide stability.
Humans need an upper limit for population, but no one person or group of people are able
to stop humans from continuing to reproduce. However, at some point in our existence, we
will encounter a lack or complete absence of some of our raw materials. Some suggest that
we have already met our upper limit. The human population with get to a place where
energy that is being harvested either runs out or will not be abundant enough to support
the entire population. When humans reach their upper limit, food sources will not be large
enough to sustain all life. Raw materials and food could be two of the bigger reasons for
death in the population. It has also been shown that there are large conflicts and war when
human population has reached or is close to reaching the upper limit.
Required Presentations:
Click on the links below to view the Module 6 presentations.
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Chapter 15
Chapter 16
Chapter 17
Optional presentation: Chapter 18