Biodiversity

History of Classification

• Biological system of classification

– Based on comparisons & hierarchical groupings

• Somewhat arbitrary
• Took several hundred years to develop

• Prior to Darwin

– Classification was concerned with describing “natural order”

• Taxonomy

– Science of describing, classifying, & organizing organisms according to their similarities & differences
• Taxonomy is traced back to Aristotle

– He arranged objects, including animals, into groups
• Used a series of “either-or” comparisons
– Object is living or non-living
• Animal or plant
• “Blooded” or “non-blooded”, etc.

• Carl von Lynne, Swedish botanist, brought simplicity & consensus to chaos in the field

– Described more than 800 species
– To each, he assigned 2 Latinized names - first name was genus name, second - species name
– This binomial nomenclature continues today

• Linnaeus recognized the need to organize species into higher taxonomic categories

• Linnaean system was widely accepted into mainstream biology

• Darwin’s theory of evolution caused reevaluation of the meaning of classification

– Before Darwin, species were fixed, immutable
– Sharing of characteristics was convenient & allowed grouping

– Darwin saw species as constantly, slowly changing
– Their sharing of characteristics makes sense because they share common ancestors

Modern Tools of Classification

• Today, modern tools give evidence of evolutionary relationships between species

– Species are now defined by ability to interbreed
– Inferring evolutionary relationships can be difficult

• Divergent evolution (hummingbirds & ostriches)
• Convergent evolution (dolphins & icthyosaurs)
• Adjustments in classifying organisms are sometimes necessary

– Snow geese & blue geese were thought to be separate species, combined into one species after inbreeding

• New technologies in molecular biochemistry making systematics more straightforward

• Relationships can be worked out by comparing proteins, RNAs, & DNAs

Early Days of Classification

• Taxonomists put organisms in series of hierarchical groups

– Called taxa (taxon, sing.)

• At first, there were thought to be only 2 kingdoms (animals & plants);

– Now there are at least 6

• In late 1960s, it was suggested to create new kingdoms

– Purpose: accommodate exceptions - five kingdom phase

– Kingdom Protista includes Euglena & all similar one-celled organisms
– Kingdom Monera proposed to accommodate bacteria or single-celled prokaryotes
– Kingdom Fungi was proposed in 1969 by R. H. Whitaker

Still there were exceptions that did not fit into any kingdom, such as green algae, thus, a new taxonomic category was developed – the domain (most inclusive)

The Three Domains

• Domain Archaea

• Includes newly discovered cell types
• Contains 1 kingdom – the Archaebacteria

• Domain Bacteria

• Includes other members of old kingdom Monera
• Has 1 kingdom – the Eubacteria

• Domain Eukarya

• Includes all kingdoms & organisms
• Composed of eukaryotic cells

– Protists
– Fungi
– Animals
– Plants

Categories within Kingdoms

• Kingdom are divided into groups called phyla

– Phyla are subdivided into classes

• Classes are subdivided into orders

– Orders are subdivided into families

» Families are divided into genera

Genera contain closley related species

Humans are Homo sapiens

Modern Classification

• System is focused on interpretation

– Taxa indicate evolutionary relationships
– Those only sharing domains are distantly related
– Relationships denote evolutionary history
– If organisms stop sharing taxa, then they stop sharing ancestors

The Origin of Life

Early Speculations

• Early speculations lacked experimental evidence

– A. Oparin, 1920s & J. Haldane, 1930s reasoned Earth’s early atmosphere was different from today’s

– Envisioned a variety of energy sources on primitive Earth (earthquakes & lightnings)

– H. Urey & S. Miller, 1952

• Built apparatus modeling Oparin-Haldane atmosphere
• Resulted in spontaneously produced organic compounds

• More circumstantial evidence accumulated

– Astronomers found simple organic compounds in meteorites

– They were convinced that Earth’s initial atmosphere could not have matched Oparin-Haldane’s model

– Fossils of ancient bacteria (3.5 billion years old) were found in Australia

– Suggested life may have evolved rapidly in less than a billion years

What are the possible scenarios?

– When ocean tidal pool evaporates salts get highly concentrated
– Could have happened in ancient oceans

• Concentrating amino acids, may allow protein to form
– Over hundreds of millions of years, similar processes could have filled oceans with proteins, carbohydrates, phospholipids, nucleotides

• Phospholipids arrange themselves into bubbles

– Chemicals could be concentrated in bubbles (might contain protein, etc.)
– These bubbles would persist aided by natural selection
– Eventually they reach a level of complexity called protocells (not living)
• Still can’t reproduce, no DNA

• Is DNA essential?

– Scripps Institute, 1993 found small molecules of synthetic RNA that within an hour began making copies of itself & the copies made more copies
– Then copies began to change - evolve- acquiring new chemical characteristics, but not alive
– Protocells might qualify as the first cells if they have RNA that:

• Can make copies of itself & evolve
• Could synthesize enzymes capable of breaking down other organic compounds
• Could synthesize enzymes capable of building and maintaining cell membranes

– Later DNA could have evolved as method of conveniently & safely storing vital chemical info contained in cell RNA

First Cell Types

• Heterotrophic cells

– Incapable of producing their own food

• Autotrophs

– Can produce chemicals to store energy

• Chemoautotrophs

– Store energy found in certain inorganic chemicals

• Most organisms found free oxygen intolerable

– In oceans

• Organisms that built simple and complex organic compounds
• Removed CO2 from the atmosphere

– More advanced autotrophs removed most of the rest & replaced it with oxygen

– The excess oxygen changed forever chemical nature of atmosphere to today’s

Further Evolution of First Cells

• First cells, prokaryotes, were always simple in structure
• 2 - 1.5 billion years ago a new cell appeared – eukaryotes

– Had membranes to isolate certain chemical reactions

• Cellular life then evolved into what we know today

• Directly related to oldest organisms on earth
– Have had lots of time to evolve & differentiate
• Thrive nearly everywhere
– Depths of oceans & Earth, all surfaces

Archaea & Bacteria Domains

• Common characteristics:
– All are single-celled organisms without nuclei
– Their DNA is contained in single, twisted, circular chromosome floating free in cytoplasm
– All have relatively thick cell walls
• Many form spores under intolerable environmental conditions, lose most of cytoplasm, shrink, get inactive until conditions improve
• As spores, very light, float in air, occur everywhere

Uses of Bacteria

• Sources of food
• Biological control of pests
• Agents of fermentation
• Making of foods & antibiotics
• Bacteria & fungi are main decomposers of dead organic matter

– Return nutrients to environment

· Characteristics

• Most are heterotrophs
• Most are decomposers
• A few are pathogens – Cause diseases in nearly every organism
• Some live as mutualistic symbionts, as in nitrogen fixation
• Some are autotrophs
• Some are chemoautotrophs

Archaea & Bacteria Domains

The Phyla

• Phyla of the Eubacteria - Cyanobacteria & Proteobacteria

• Cyanobacteria

– Named for their blue-green pigment, more than 1,500 species

• Proteobacteria -

– The true bacteria, display one of three body shapes

– A sphere of coccus, a rod of bacillus, a spiral or helical shape

• Kingdom Archaebacteria

– Prokaryotes that many believe are the most ancient group of living organisms
– Characterized by their ribosomal RNA, lipid structure, & certain enzymes
– Inhabit extreme environments, such as hot springs, sea vents, boiling muds
– Originally placed with Monerans
• Now enjoy their own kingdom

Domain Eukarya

Kingdom Protista

• What is a protist?

– Some are animal-like, others are plant-like, some are fungus-like

– Most are unicellular, lack tissues, seldom demonstrate specialization

• Prostita - Algae

– Autotrophic
• Trap light with chlorophyll
• Found in aquatic environments where they perform ecological functions

• Protozoans (first animals)

– Heterotrophs
• Single-celled eukaryotes
– No cell walls, no chlorophyll
– Found in fresh & marine waters

• Slime molds

– Heterotrophic protists

• Start life as single-celled
• At times organize selves into multicellular organisms

Domain Eukarya

Kingdom Fungi

• Major traits

– All eukaryotic
– Mostly multicellular, heterotrophic
– Thick walls are made of chitin
– Decomposers
– Cause human disease of lungs and skin

Domain Eukarya

Kingdom Plantae

• General traits

– Eukaryotic cells are surrounded by thick cell walls
– Multicellular, autotrophic
– Have alteration of generations life cycle
– Extremely diverse in structures
– Among the first organisms to live out of water
– All cells must have nutrients & oxygen

Domain Eukarya

Kingdom Animalia

• General traits

– All are multicellular
– Eukaryotic heterotrophs
– Diverse group of organisms

– Evolutionary trends

• Development of symmetry
• Formation of a body cavity (coelem)
• Fate of the first opening in the embryo

• Animals respond quicker to sudden changes in environments

– Animals move around more
– However, not all of them are mobile
– Sponges & mollusks stay put most of their lives

• Structure of animals is more fixed

– All mammals have 4 limbs
– All insects have 6 limbs
– Plants grow a little each year
– Animals have little or no growth as adults

• All terrestrial organisms face problems associated with limited H2O

– Animal cells quickly lose water when exposed to dry air

• Refinement of physiological systems

– Nervous system becomes netlike in jellyfish
– Brains become increasingly complex

The Phyla of Kingdom Animalia

• Porifera

– Sponges, multicellular, most primitive

• Cnidaria

– Have radial symmetry & defined tissues

• Platyhelminthes

– Flatworms, posses bilateral symmetry

• Nematoda

– Roundworms
– Bilateral symmetry
– Most abundant animals on Earth

• Mollusca
• Annelida

– First animals to demonstrate true segmentation
– Have bilateral symmetry & coelem

• Arthropoda

– Named for their joined appendages
– Have bilateral symmetry & coelem

• Echinodermata

– Bilateral symmetry as larvae & radial symmetry as adults, have a coelem

• Chordata

– Possess bilateral symmetry, & coelem

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