1. Biological Classification- How Many Species Exist?
Biodiversity is the variety within and among living species.
Number of species known to science is between 1.4 and 1.8 million
Uncertainty due to differences in methods of storing and describing specimens
Total number of species – estimates range from 3 – 100 million
Average estimate is ~10 million species on Earth

2. Biological Classification - How Many Species Exist?
Systematists are scientists who specialize in describing and categorizing organisms.
They work in the field of biological classification.
Biological collections such as natural history museums and herbaria store samples of the different species.
Systematists evaluate these collections to determine overlap in identifying of species.

3. Biological Classification - Kingdoms and Domains
Modern species are divided into three large groups, or domains.
Bacteria, Archaea, and Eukarya
Within Eukarya, four kingdoms are also recognized
Plantae
Animalia
Fungi
Protista

4. The tree of life. Eukarya Protista Bacteria Archaea Plants Fungi
Animals
Present time
More recent divergence
Time
Divergence early in life’s history
4 billion years ago

5. Biological Classification - Kingdoms and Domains
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6. Biological Classification - A Closer Look: Kingdoms and Domains
Recently, some scientists have begun to suggest that organisms should be classified based on evolutionary relationships.
Major groups under this system correspond to divergences early in life’s history.
Determining evolutionary relationships requires comparing DNA.
DNA of closely related organisms should be more similar than DNA of distantly related organisms.

7. Biological Classification - A Closer Look: Kingdoms and Domains
Using rRNA to determine relationships among distantly related organisms

8. Animation: The Tree of Life
Click “Go to Animation” / Click “Play”

9. The Diversity of Life - Bacteria and Archaea
Life on earth arose at least 3.6 million years ago, according to the fossil record.
Most ancient fossilized cells are very similar to modern bacteria and archaea
Prokaryotes like bacteria and archaea don’t have a nucleus, lack mitochondria and chloroplasts, and most are unicellular
Incredibly numerous and diverse
Found on every square centimeter of the earth’s surface, even inside deep sea vents, far underground, and in clouds
Prokaryotes are called microbes and are studied by microbiologists.

10. Domain Bacteria Most bacteria are probably harmless to humans.
We are most familiar with the ones that cause disease
Many known bacteria obtain nutrients by decomposing dead organisms
Competition between bacteria has produced compounds that humans make use of.
Antibiotics – ~50% of antibiotics are derived from bacterial sources
Restriction enzymes – proteins that chop DNA at specific sequences; useful in biotechnology

11. Domain Archaea Superficially similar to bacteria
Differ in structure of cell membranes
Archaeans typically found in extreme environments (high temperature, high pressure, high salt concentration)
Taq polymerase comes from an archaean, Thermophilus aquaticus
Archaeans are likely to be source of other interesting biomolecules

12. The Diversity of Life – Domain Eukarya
Evolution of the Eukaryotes
Protists are the simplest of the eukaryotes
Oldest eukaryotic fossils are ~2 billion years old, 1.5 billion years later than the first prokaryotic cells
Endosymbiotic theory explains the evolution of eukaryotes and their specialized structures.

13. The Diversity of Life – Evolution of Eukaryotes
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Endosymbiotic Theory

14. The Diversity of Life – Protista
Modern protists contain members that resemble animals, plants, and fungi.
Most members of the kingdom are not known
Protists are eukaryotes that don’t belong in Kingdom Fungi, Kingdom Plantae or Kingdom Animalia
Protists can be heterotrophic or autotrophic
Heterotrophic – protozoans
Some of these can cause disease
Autotrophic
Multicellular – “seaweeds”
Unicellular - phytoplankton

15. The Diversity of Life – Protista
The Diversity of Protists:
Ciliates, flagellates, amoebas, diatoms, algae, slime molds

16. The Diversity of Life – Protista
Bioprospectors have examined the plant-like protists most closely for useful compounds.
Natural selection has driven the evolution of defensive compounds in these organisms.
Extracts from red algae might be used in anti-viral medication.
Carageenan, a stabilizer and thickener, also comes from protists.

17. Chondrus crispus, a red alga that is the source of carageenan
(a) Animal-like protist
(b) Fungus-like protist
Mattesia oryzaephili is a parasite that infests and kills beetles in stored grain. M. oryzaephili may be useful in
controlling these pests.
Lagenidium giganteum, sprayed on ponds to control mosquito populations
(c) Plant-like protist
(d) Plant-like protist
Gonyaulax polyedra, a luminescent alga used to measure levels of toxic materials in ocean sediments
Chondrus crispus, a red alga that is the source of carageenan

18. The Diversity of Life – Animalia
Animals comprise a wide range of organisms, but all share a common set of characteristics.
Multicellular
Heterotrophic (must eat to get energy)
Mobile during at least one stage of life
By 530 million years ago, all modern animal groups were present.
Most appeared quickly in fossil record
Multicellular organisms quickly proliferated
Known as Cambrian explosion

19. The Diversity of Life – Animalia
A sampling of animal diversity

20. 13.2 The Diversity of Life – Animalia
A sampling of animal diversity

21. The Diversity of Life – Animalia
Most bioprospecting work focuses on invertebrates.
Vertebrates only account for ~4% of animals
Think about how many insects there are compared to us; think about how many worms there are compared to us
Invertebrates are far more numerous and diverse
Many invertebrates produce compounds found nowhere else in nature

22. The Diversity of Life – Animalia

23. The Diversity of Life – Fungi
Fungi characteristics
Immobile
Many reproduce by releasing spores
Heterotrophic
Feed by means of hyphae
The hyphae of fungi can extend over a very large area
DNA analysis by mycologists indicates fungi is more closely related to animals than to plants

24. The Diversity of Life – Fungi
Fungi are grouped on the basis of spore formation

25. The Diversity of Life – Fungi
Commercially important fungal forms
Yeast is a single celled type of fungi that is used in bread, wine, and beer making.
Mold is quickly reproducing and fast growing to produce flavorful cheeses
Fungi produce a number of important drugs
Antibiotics
Cyclosporin
Statins

26. The Diversity of Life – Plantae
Characteristics of Plantae
Multicellular
Eukaryotic
Autotrophic (manufacture own food) via photosynthesis

27. The Diversity of Life – Plantae
Plants have been present on land for ~400 million years.
First plants were low to ground, lacked vascular tissue
Evolution of vascular tissue for water and nutrient transport
Allowed growth to tree size
Allowed growth in drier areas
Most modern plants in group only ~140 million years old
Flowering plants

29. Diversity of flowering plants.
(a) Foxglove (Digitalis purpurea)
(b) Aloe (Aloe barbadensis)
(c) Willow (Salix alba)
Source of heart drug digitalis
Source of aloe vera, used to treat burns and dry skin
Source of aspirin

30. The Diversity of Life – Plantae
Over 90% of modern plants are flowering plants and many specializations
Rapid increase of flower plant species is called adaptive radiation.
Flowering plants employ double fertilization method or reproduction
Also often involve animals in reproductive process (pollination) – lots of coevolution has happened with flowering plants and animals that eat them
Also synthesize many secondary compounds that deter predators

31. The Diversity of Life – Plantae
Kingdom Plantae is the source of many drugs and compounds.
Source of most naturally derived drugs
Aspirin, Digitalis, Morphine, and Caffeine
Pharmaceutical manufacturers reproduce hundreds of compounds first found in plants

32. The Diversity of Life - Viruses
A virus consists of a strand of DNA or RNA
Viruses hijack transcription machinery of cells to reproduce
Once hijacked cell cannot perform own functions
HIV, smallpox, polio, influenza are all caused by viruses
Figure 12.18

33. Animation: Endosymbiotic Theory
Click “Go to Animation” / Click “Play”

34. Learning About Species - Fishing For Useful Species
The National Cancer Institute has employed a brute-force approach to looking for anti-cancer compounds
Receive specimens from around the world, extract materials and screen against cancer cell lines
One major compound, Taxol, has been identified using this technique
Isolated from Pacific yew tree, a mitotic inhibitor used as cancer medication

35. Learning About Species – Understanding Ecology
Understanding an organism’s ecology—how it lives in its environment—can be helpful in evaluating potentially beneficial compounds.
Survival in extreme environments
High levels of competition with bacteria and fungi
Susceptibility to predation
Ability to live on or in other organisms
Survival in high population densities

36. Learning About Species – Reconstructing Evolutionary History
A classification system reflecting evolutionary relationships is more useful to scientists.
An organism’s chemical traits will probably be similar to those of its closest relative
If looking for new compounds, could begin by screening close relatives of organisms already known to produce compounds

37. Learning About Species – Reconstructing Evolutionary History
The challenge in making an evolutionary classification is that organisms do not always resemble their closest living relatives.

38. Learning About Species – Developing Evolutionary Classifications
An evolutionary classification of sparrows

39. Learning About Species – Developing Evolutionary Classifications
Reconstructing evolutionary history not always as easy as the sparrow example.
Can be confounded by loss of traits, and convergence
DNA provides a means of testing evolutionary hypotheses

40. Learning About Species – Testing Evolutionary Classifications
Scientists can test evolutionary hypotheses with data from fossils and from living organisms.
Fossils provide information about the genealogy of different living groups
Comparison of DNA from living organisms can also validate or refute proposed classifications
DNA can give clues to near relatives, but lab process can take time

41. Learning About Species – Learning From the Shamans
Often local people in biologically diverse areas make extensive use of naturally occurring products.
Shamans often have much knowledge of locally useful compounds.
Biopiracy is when local knowledge is used without benefiting local people.
UN Convention on Biodiversity is supposed to address this.
Our biodiversity represents an enormous potential, but only if we recognize its value.

42. Overview of Classification
Domain Bacteria – prokaryotic
Bacteria we are familiar with
Domain Archaea – prokaryotic
Includes extremophile bacteria
Domain Eukarya – eukaryotic
Includes protists, fungi, plants, animals