Biology 100/101
Lecture 21
Biodiversity I
(Print Version)

Announcements

Objectives

Web Resources

What is Biodiversity?

Genetic Diversity

Lecture Activity

Species Diversity

Ecosystem Diversity

Reduction of Biodiversity

Model of Biodiversity

Lecture Syllabus

IB 100/101 Home Page

Announcements

Text Readings in
Lewis et al.		 Testing Your Knowledge Thinking Scientifically
Chapter 45, Environmental Challenges No questions today No questions today

Information on the topic of biodiversity is presented in several different sections of your text, from chapter opening vignettes to boxed readings. Explore your text to discover these readings!

You may also ask questions and see answers to your classmates' questions in Web Crossing in the "Talk to Jim, Jason, and Ed" discussion.

Objectives:

After studying this material you should be able to:

  1. Define the term biodiversity and explain how the three levels of biodiversity (genetic diversity, species diversity, and ecosystem diversity) are related and dependent on one another.

  2. Describe the roles of sexual reproduction, meiosis, and mutation in the origin and maintenance of genetic variation in a population.

  3. Define what a species is and discuss why the definition is important.

  4. Have a basic working knowledge of the number of species known, the estimated number in existence, and how these numbers are distributed among the major groups of organisms.

  5. Explain how biodiversity is lost and how rapidly it is currently being lost.

  6. Know these terms and understand their relationships:

    7. biodiversity genetic variability species variability
    ecosystem variability infraspecific variability population
    sexual reproduction alleles mutations
    species invasive species species loss
    archaea bacteria eukarya
    mass extinction population loss habitat loss

Web Resources:

What is Biodiversity?

Biodiversity (=biological diversity) is defined at three levels: genetic diversity, species diversity, and ecosystem diversity.

Biodiversity increases when new genetic variation is produced, a new species arises, or a novel ecosystem (or habitat) is formed.

Biodiversity decreases when the genetic variation within a species decreases, a species becomes extinct, or an ecosystem (or habitat) is lost.

Biodiversity is a dynamic process, and what we see now is the product of hundreds of millions of years of evolutionary history.

Genetic Diversity

The variety of genetic information contained in all of the individual plants, animals, and microorganisms in the world.

It occurs between species, as well as within and between populations of the same species. Individuals belonging to the same species are usually not identical genetically.

Differences in the amount and distribution of genetic variation within a single species can be attributed to the enormous variety and complexity of habitats, and the different ways organisms have adapted to these habitats.

Genetic diversity can be measured using a variety of DNA and protein-based techniques to determine genotypic differences.

It can also (in part) be catalogued based on differences in expressed, phenotypic traits. (For example, of all the genes in humans, 10,000 are outwardly (visibly) expressed and vary from person to person. Such phenotypic differences include differences in race, eye color, height, etc.)

Lecture Activity

As a review for the upcoming exam, consider the following questions:

  1. What are the sources of genetic variation in a population?
  2. How does new genetic variation arise?
  3. How does genetic variation spread through a population?

Species Diversity

The variety of living species.

The question "What is a species?" is not readily answered, and many definitions exist.

Systems for the classification of species go back at least 2,500 years to the Greeks (Aristotle and Plato).

The biological species concept and some recently proposed alternatives

Lewis et al. define a species as "a group of similar individuals that interbreed in nature and are reproductively isolated from all other such groups." Another definition describes species as being characterized by a unique diagnosable character. Differences of opinion in defining species leads to drastic difference in estimated numbers of species.

Very simply, species are the different "kinds" of living or extinct organisms that we, as humans, can define and comprehend.

An estimated 1.7 million species have been described to date.

Estimates for the total number of species vary from 10 to 50 million (and perhaps up to 100 million).

Classification of Life: All life is grouped into three domains:

    Bacteria (the "prokaryotes"), 4000 species.

    Archaea, 500 species. The Archaea were discovered by Dr. Carl Woese of UIUC!

    Eukarya (the eukaryotes), 1,700,000 species. The Eukarya includes the protists, plants, fungi, and animals (traditionally considered kingdoms).

Species diversity is not evenly distributed across the globe. In general, species richness is concentrated in equatorial regions (tropical rainforests) and decreases as one moves to the poles (or increases in altitude). 40-50% of all species are found in wet tropical rainforests, a region that comprises only 2% of the Earth's land surface.

Of 250,000 flowering plant species described, 125,000 are found in three tropical countries: Brazil, Zaire, and Indonesia. For comparisons, 18,000 are found in the U.S. (incl. Hawaii and Puerto Rico) and about 2,000 in Illinois.

How many species are there? How many have yet to be described?
(Some examples from: Systematics Agenda 2000: Charting the Biosphere.)

Number Described Estimated to be Discovered
Viruses 5,000 about 500,000
Bacteria 4,000 400,000-3 million
Fungi 70,000 1-1.5 million
Protozoans 40,000 100,000-200,000
Algae 40,000 200,000-10 million
Flowering plants 250,000 300,000-500,000
Vertebrates 45,000 50,000
Roundworms 15,000 500,000-1 million
Mollusks 70,000 200,000
Crustaceans 40,000 150,000
Spiders and mites 75,000 750,000-10 million
Insects 950,000 8-100 million

Numbers are approximate. Almost 60% of all species described have been insects.

Two new primate species discovered in the Amazon in 2002

New fish species discovered in Texas in 2004! To see pictures of the fish, there is a gray box towards the bottom of the page with a link.

Census of Marine Life. First report: Oct, 2003.

All Species Inventory, brought to you by the All Species Foundation. Their goal is to complete an inventory of all species of life on Earth within the next 25 years -- a human generation.

For additional information:

Ecosystem Diversity

The variety of habitats, biological communities, and ecological processes (the interactions among species and between species and their environment) occurring within and between each type of ecosystem.

Ecological processes, such as water and nutrient cycling, energy flow, succession, predation, competition, parasitism, primary production, decomposition of organic matter, soil rehabilitation, pest and disease regulation, water quality, and pollination, are maintained by a wide range of biologically diverse populations in natural ecosystems.

Ecosystem diversity is harder to measure than species or genetic diversity, partly because ecosystems themselves are harder to define.

Ecosystem diversity is a precondition for species and genetic diversity.

For additional information:

Reduction of Biological Diversity

Recall, biodiversity decreases when a species becomes extinct, the genetic variation within a species decreases, or an ecosystem (or habitat) is lost.

We are in a biodiversity crisis--the fastest mass extinction in Earth's history!

While extinction is a natural process, the alarming rate of extinction today is specifically human-induced and unprecedented.

This is largely due to: human alteration or destruction of habitats, the introduction of alien species, overexploitation of species and natural resources (hunting, fishing, pet trade), human overpopulation, the spread of agriculture, pollution.

1. Species Loss (Extinction)

  • Extinction is accelerating. The rate of species extinction is 1,000-10,000 times higher now than at any time before humans evolved.

  • 20% of all bird species have gone extinct during the last 2000 years and 11% more are endangered now. In the US, over the last 100 years, 2% of the amphibians, 1.2% of the fish, 1% of the plants, and 9% of the freshwater mussels have vanished. Note that these are all species easily observed and recorded. Other losses are unknown.

  • These losses are numerically comparable to those in the 5 mass extinctions that occurred on earth during the last 500 million years. The last one was the end of the reptiles, 65 million years ago. Most significant, however, is that humans are responsible for this one, and its rate is much faster than any prior mass extinction (a few decades to centuries vs. millions of years).

  • About 30,000 (other estimates up to 50,000) species go extinct annually. This translates to three to six species per hour!

  • Losses of biodiversity are irreversible. Replacement of the number of species (though not the same ones) takes approximately 10 million years.

  • Conservation measures, sustainable development, and stabilization of human population numbers and consumption patterns seem to offer some hope that the next mass extinction will not result like previous ones, when 90% of the world's species were lost.

  • In Illinois, 329 species of flowering plants are threatened or endangered. One species is extinct: Thismia americana.

  • For additional information:

2. Population Loss (Loss of Genetic Variation)

3. Habitat Loss

  • About 95% of all the tropical forests which existed 100 years ago are now gone. Now, 1-2% of the remaining tropical forests are removed each year. This is equivalent to losing an area the size of Florida every year!

  • This translates to about 2.4 acres (1 hectare) per second, equivalent to two football fields (or 149 acres per minute or an area larger than NYC every day)

  • If deforestation continues at current rates, it is estimated that all tropical rainforests will be destroyed by the year 2030.

  • Habitat loss directly impacts species diversity and genetic diversity

  • For additional information:

    • For a discussion on rates of extinctions, especially in the tropics, check out the Rainforest Action Network for rates of rainforest destruction.

    • Prior to settlement, more than 60% of Illinois, approximately 22 million acres, were covered with prairie. Today, just over 2,000 acres of high quality prairie remain, less than one-hundredth of one percent. Tall grass prairies are endangered ecosystems in Illinois. The Tallgrass Prairie in Illinois, by Ken Robertson, INHS.

Model of Biological Diversity

A Model of Biodiversity to pull it all together.

Illinois Biodiversity

INHS has several resources to explore biodiversity in Illinois