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Biological Communities - Symbiosis, Niches, and Biomes



Ecology, Symbiosis, Competition For Resources, Niches, Biodiversity, and Biomes

Biology is the study of living things.

Ecology is the branch of biology that studies the relationships between organisms and their environments.

This biology resource page will focus on ecology and will cover:

* symbiotic interactions between species (mutualism, parasitism, and commensalism),

* niches,

* biodiversity,

* competition for resources between species, and

* biomes.

The image to the left is of some Clown Fish and Sea Anemones. Clown Fish and Sea Anemones engage in a mutualistic relationship as both benefit from living together. The Clown Fish benefits because the Sea Anemone keeps the Clown Fish safe from other fish. (Sea anemones are poisonous to most other organisms, but not to Clown Fish, therefore Clown Fish are safe from other fish while within the arms of the anemone.) The anemone benefits both by getting free "fertilizer" from the Clown Fish, and by being keep safe from certain other types of fish as the Clown Fish chases them away.

Our homeschool co-op is participating in a high school level class in biology this year. We use Holt Biology as the core of our curriculum, and add biology youtubes, labs, games, and other biology resources to enrich our study. This page is a collection of those additional resources for chapter 17 in Holt Biology on "Biological Communities." (I will be adding more to this page over time, so please check back again!)

Holt Biology - This is the text that we're using along with the biology resources on this page for our homeschool co-op's biology class.

Holt Biology comes in CD, as well as a hardback version. You can purchase either version by visiting the link below.

Symbiotic Relationships - How Organisms Interact in Communities - 17.1 in Holt Biology

1. Watch the three youtubes below. The first one is a movie (rather than just a collection of still pictures) and shows some interesting animal interactions! The second one is Paul Anderson's very helpful video he made for his students. The third one also teaches about mutualism, commensalism, and parasitism, and even gives a quiz at the end to see if you've learned what each means!

2. Read section 17.1 on "How Organisms Interact in Communities" in your text.

3. Answer the review questions in the text.

4. Study the vocabulary words (see below).

How Organisms Interact In Communities - 17.1 in Holt Biology

Vocabulary Words To Know

  • Coevolution - When two species have evolved together in such a way that they both are of benefit to each other, we call this coevolution. An example is the bat and flower pictured in section 16.1 in our book. The flower provides food for the plant, and in turn the bat's wings aid in pollinating the plant.
  • Predation - is related to the word "predator" and means the act of one organism killing and eating another.
  • Secondary compounds - Theses are chemicals that some plants use to discourage animals from eating them. What is toxic to many insects is not always toxic to all though. Some animals have developed ways of eating a particular plant without being bothered by the chemicals.
  • Symbiosis - is where two or more species live together. These relationships can be of benefit to both organisms, or only to one. If they are of benefit to only one organism, the other may be either unaffected by their relationship, or harmed by it.
  • Mutualism - if both organisms benefit from the relationship, it's called mutualism.
  • Parasitism is related to the word "parasites." In parasitism, one species not only feeds off, but also usually lives on (or in), another species. They don't kill their prey in order to eat them. Ticks, mosquitoes, fleas, and hookworms are all parasites. Parasitism is a type of symbiotic relationship in which one of the organisms is harmed by the other.
  • Commensalism -is the type of symbiotic relationship in which one organism benefits and the other is unaffected.
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How Competition Shapes Communities - 17.2 in Holt Biology

1. Start this video around 2:50 to learn about fundamental niche, realized niche, competitive exclusion, and resource partitioning.

2. Read section 17.2 , "How Competition Shapes Communities," in your text.

3. Answer the review questions in the book.

4. Study the vocabulary (see below).

How Competition Shapes Communities - 17.2 in Holt Biology

Vocabulary Words To Know

  • Competition is where two species use the same resource, such as food, light, water, nesting sites, living space, and nutrients. In other words, the two species "compete" for that resource.
  • Niche - this is the "job" a particular organism performs within an ecosystem. A niche includes all the ways the organism interacts with its environment (what it eats, when it hunts, etc.). An excellent description of a niche, along with examples, can be found at: The Ecological Niche.
  • Fundamental niche - all the resources available to a species. The fundamental niche includes not only the resources a species actually uses, but also what it could use but doesn't. The example in our text is of the bird who only eats insects at the top of spruce trees, even though those same insects are found elsewhere on the tree as well. In this case, the fundamental niche would include all the insects anywhere on the tree.
  • A realized niche is smaller than a fundamental niche. The realized niche is only the part of a resource that the species actually uses. In the example in the book, all five species of Warblers ate insects from a different part of the tree, so although they shared the same fundamental niche, each had their own unique realized niche.
  • Competitive exclusion - this is where two species are competing for a resource and the one that uses the resource less efficiently often dies out. In order to avoid competition exclusion, some species may divide the resources in such a way that they are no longer competing. Because the 5 species of birds in the example above were eating insects from different parts of the tree, they were not competing for food.
  • Biodiversity - this refers to the variety of organisms living in a community. Predation can increase biodiversity because it reduces competition between species (and thus reduces the likelihood of competition exclusion.)


Terrestrial Biomes - 17.3 - Large Biological Communities are called Biomes.

Rainforest Biome

Rainforest Biome

Tropical Rainforest Biome

Savanna Biome

Taiga Biome

Yukon River

Yukon River

Another image of the Taiga Biome



Tundra Biome

Another image of the Tundra Biome

California Desert

California Desert

Desert Biome


Temperate Grassland Biome

Rhineland Germany

Rhineland Germany

Temperate Deciduous Forest Biome

Temperate Evergreen Forest Biome

Photo credits:

photo of Temperate Grassland Biome by Dustin M. Ramsey

Biomes - 17.3

You've now finished this section on Biological Communities! - You're ready for the next section on:

  • Global Changes And The Environment
    This page covers topics such as acid rain, global warming and the greenhouse effect, the ozone layer, chemical pollution, the loss of topsoil, and the human population growth rate.


List of pages in this series

Homepage: Biology: Information, Videos, and Labs

Unit 1 on Cell Biology

Biology Labs, Activities, Videos, and Study Guides About Cells (Photosynthesis, Mitosis, Cell Organelles, and More)

Unit 2 on Genetics

Labs, Information, And Videos For High School Students Studying Genetics.

Unit 3 on The History of Life on Earth

The History Of Life On Earth.

Unit 4 on Ecology

Ecological Principles / Populations


Biological Communities - Symbiosis, Niches, and Biomes

Global Changes And The Environment

Unit 5 on Diversity

An Introduction to Taxonomy - The Kingdoms and Domains Of Life

Learning About Viruses And Bacteria

Protists: Paramecium, Amoebas, Algae, Diatoms, Euglena, and Others

The Fungi Kingdom

Unit 6 on All About Plants

The Plant Kingdom

Unit 7 on The Animal Kingdom: Invertebrates

The Animal Kingdom - An Introduction

Sponges are Simple Animals

The Cnidarians: Jellyfish, Sea Anemones, Hydrozoans, and Corals

Earthworms, Christmas Tree Worms, Leeches, and Other Annelids

Check back later for additional biology units!

Are you studying biology?

Guestbook - Comments? Questions?

anonymous on September 23, 2012:

Wonderful photos, I couldn't stop looking at them its like I was stuck. I especially enjoy reading about symbiotic relationships, kinda blows your mind. Humans have those right? Oh wait no we don't.

JoyfulPamela2 from Pennsylvania, USA on July 17, 2012:

Wow! I wish I would have seen this last year at this time when I was preparing my teen for biology. Wonderful material, Janeice! :)

BryanLSC on April 21, 2012:

@JanieceTobey: A thousand apologies, just now when I was reading it, I guess that particular image of the rainforest must have failed to load! Sigh, my faulty internet... Sorry!

JanieceTobey (author) on April 21, 2012:

@BryanLSC: Thanks for all your visits and comments on my biology pages! Yes, the rainforest is beautiful! And it's mentioned on this page. Just scroll up a little ways. It's there. :-) I wouldn't forget the rainforest!!

BryanLSC on April 21, 2012:

Temperate Deciduous Forest Biome is the best! But wait, where is the equally beautiful tropical rainforest biome?

Blackspaniel1 on December 17, 2011:


baby-strollers on December 10, 2011:

Very informative lens!

Anthony Godinho from Ontario, Canada on December 10, 2011:

You've been putting together very useful resources for your homeschool co-op. This is another great addition!

anonymous on December 09, 2011:

...I love this!

anonymous on December 09, 2011:

Another work of awesomeness that I would love to have had when I was home schooling my are definitely a teacher's teacher my dear...excellence is simply your habit in all things!

traveller27 on December 09, 2011:

Well done - blessed by a travelling angel.

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