Biology 100/101
Lecture 21
Biodiversity I
(Print Version)
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, and Ed" discussion.
Objectives:
After studying this material you should be able to:
- 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.
- Describe the roles of sexual reproduction, meiosis, and mutation in the origin and maintenance of genetic variation in a population.
- Define what a species is and discuss why the definition is important.
- 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.
- Explain how biodiversity is lost and how rapidly it is currently being lost.
- Know these terms and understand their relationships:
| 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:
- The Lorax, by Dr. Seuss. Also, see the Teacher CyberGuide, for great Dr. Seuss activities.
- An Overview of Biodiversity, from the World Conservation Monitoring Center. This is an excellent resource for biodiversity. This large file has been downloaded to our server to facilitate retrieval.
- The Biodiversity Center. A neat collection of articles on biodiversity from "Defenders" magazine. One of these articles, Seeking Meanings by Douglas Chadwick, is a nice read.
- Read "The threatened biosphere" by Edward O. Wilson, a famous Harvard biologist and author of several excellent books on biodiversity.
- Biodiversity from Okanagan, British Columbia. More general information on biodiversity.
- World Resources Institute
- The Diversity of Life from the World Resources Institute. Includes an explanation of cultural diversity.
- Biodiversity and Biological Collections Web Server
- National Biological Information Infrastructure. This is a huge database containing information on biodiversity.
- Biodiversity and Conservation, a hypertext book.
- Biodiversity and Conservation: The Web of Life, a featured program at the Field Museum of Natural History in Chicago!
- Illinois Natural History Survey. A state agency, on the UIUC campus (and where Jason Koontz works) that is charged with studying the state's flora and fauna.
What is Biodiversity?
- Definition of Biodiversity, from the World Conservation Monitoring Center. This file was copied to our server to facilitate retrieval.
- Defining the "B" word from Defenders magazine
- Definition from Defenders magazine (an essay by Douglas Chadwick)
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
- Genetic Diversity, from the National Biological Information Infrastructure
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.
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.
Lecture Activity
As a review for the upcoming exam, consider the following questions:
- What are the sources of genetic variation in a population?
- Ans: independent assortment and crossing over
- How does new genetic variation arise?
- Ans: genetic mutation generates new alleles
- How does genetic variation spread through a population?
- Ans: beneficial alleles can spread through the population through natural selection
Species Diversity
The variety of living species.
The question "What is a species?" turns out to be tricky...
Systems for the classification of species go back at least 2,500 years to the Greeks (Aristotle and Plato) and were formalized by Linneaus in the 18th century.
Lewis textbook definition is called the biological species concept
"a group of similar species that interbreed in nature and are reproductively isolated from all other such groups"
A less restrictive (more pragmatic) definition is the phylogenetic species concept
"The irreducible group of common ancestry which are diagnosably distinct from all other such groups"
An estimated 1.7 million species have been described to date.
How many do you think have NOT been described?
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.
Ecosystem Diversity
The variety of habitats, biological communities, and ecological processes 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 a precondition for species and genetic diversity.
Reduction of Biological Diversity
Mass extinctions have re-set the level of biodiversity on earth through deep time.
Figure 16.15 (early extinctions) and Figure 16.15 (later extinctions)
We are in a biodiversity crisis--the SIXTH and FASTEST mass extinction in Earth's history!
Guess who's responsible...
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.
- 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:
- Endangered or
threatened species in the U.S.
- Endangered
or threatened species in Illinois
- The
Sixth Extinction, by Niles Eldridge. An excellent read!
- Recorded
Extinctions, by Peter Bryant
- Extinction of the dinosaurs
2. Population Loss (Loss of Genetic Variation)
- The decline in numbers and sizes of populations.
- Potential for inbreeding and lack of variety in mate selection.
- Invasive Species, from USDA and More on invasive species, from the US Geological Survey.
- Loss of genetic diversity in Illinois populations of the Greater Prairie Chicken.
- UIUC's Head of Animal Biology, Ken Paige, has been studying the genetics of the Greater Prairie Chicken.
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