Chapter 13

Prospecting for Biological Gold Biodiversity and Classification

 

13.1 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

 

13.1 Biological Classification - Kingdoms and Domains

¤ Modern species are divided into three large groups, or domains.

¤ Bacteria

¤ Archaea

¤ Eukarya

 

¤ Within Eukarya, four kingdoms are also recognized

¤ Plantae

¤ Animalia

¤ Fungi

¤ Protista

 

13.1 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 lifeÕs history.

¤ Determining evolutionary relationships requires comparing DNA.

¤ DNA of closely related organisms should be more similar than DNA of distantly related organisms.

 

¤ Using rRNA to determine relationships among distantly related organisms

 

13.2 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

¤ Prokaryotic – bacteria and archaea donÕt have a nucleus, and also lack mitochondria and chloroplasts

¤ Most are unicellular

¤ Incredibly numerous and diverse.  Found on every square centimeter of the earthÕs surface, even inside deep sea vents, far underground, and in clouds.

 

¤  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

 

¤ 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

 

13.2 The Diversity of Life - Protista

¤ 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

 

¤ Modern protists contain members that resemble animals, plants, and fungi

¤ Most members of the kingdom are not known

¤ No agreement among scientists on number of groups below kingdom

¤ Number of proposed groups ranges from 8 to 80

 

¤ 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, stabilizer and thickener, also comes from protists

 

13.2 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

 

¤ Most bioprospecting work focuses on invertebrates

¤ Vertebrates only account for ~4% of animals

¤ Invertebrates are far more numerous and diverse

¤ Many invertebrates produce compounds found nowhere else in nature

 

13.2 The Diversity of Life - Fungi

¤ Fungi characteristics

¤ Immobile

¤ Heterotrophic

¤ Feed by means of hyphae

¤ DNA analysis indicates fungi is more closely related to animals than to plants

 

¤ The hyphae of fungi can extend over a very large area

 

¤  Fungi are grouped on the basis of spore formation

 

¤ Fungi produce a number of important drugs

¤ Antibiotics

¤ Cyclosporin

¤ Statins

 

13.2 The Diversity of Life - Plantae

¤ Characteristics of Plantae

¤ Multicellular

¤ Eukaryotic

¤ Autotrophic (manufacture own food) via photosynthesis

 

¤ 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

 

¤ 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)

¤ Also synthesize many secondary compounds that deter predators

 

¤ Double fertilization

 

¤ Kingdom Plantae is the source of many drugs and compounds

¤ Source of most naturally derived drugs

¤ Aspirin

¤ Digitalis

¤ Morphine

¤ Caffeine

¤ Pharmaceutical manufacturers reproduce hundreds of compounds first found in plants

 

13.2 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

 

13.3 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

 

13.3 Learning About Species - Understanding Ecology

¤ Understanding an organismÕs 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

 

13.3 Learning About Species - Reconstructing Evolutionary History

¤ A classification system reflecting evolutionary relationships is more useful to scientists

¤ An organismÕs 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

 

¤  The challenge in making an evolutionary classification is that organisms do not always resemble their closest living relatives

¤  New World vultures are more closely related to storks than they are to Old World vultures

 

13.3 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

 

13.3 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 supports vulture classification, but does not support sparrow classification

¤ DNA can give clues to near relatives, but lab process can take time

 

13.3 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.