Classification of Organisms In 1735 Linnaeus developed the

Classification of Organisms In 1735 Linnaeus developed the following hierarchical taxonomic classification § Kingdom - Animalia § Phylum - Chordata § Class - Mammalia § Order- Primates § Family - Hominidae § Genus - Homo § Species - sapiens

By hierarchical we mean that the highest categories (Kingdoms) contain many sub-categories, etc. By taxonomic we me organisms are grouped together according to the similarity of their organ structure and function. You can imagine the classification scheme of life as a giant “tree of life”. The trunk would split into five great branches: the kingdoms of life. Each great branch would split into dozens of smaller branches : phyla Each phyla branch would split into dozens of classes, and so forth. At the edges of the tree would be millions of tiny twigs: species.

So let’s explain the classification chain for humans: Kingdom – Animalia: means we are not bacteria, amoebae, plants or fungi (these are members of the other four kingdoms) Phylum – Chordata: means we are among those animals with spinal columns. Excluded would be animals like garden slugs, insects, clams, and coral. Class-Mammalia: means we are warm blooded, have hair, give birth to live young, etc. Excluded would be the other classes of animals with spinal columns: fish, amphibians, reptiles, and birds.

Order-Primates: This group includes tarsiers, monkeys, gibbons, the great apes including humans. Family-Hominidae: This would include the great apes: orangutans, gorillas, chimpanzees, humans Genus-Homo: Presently we are the only species in the genus (big foot? ), but 40, 000 years ago or so there were beside us: Homo Neanderthalis, Homo florensis (the “hobbit”), Homo denosovan, and Homo erectus (? ) Species- sapiens Now don’t panic. Just be familiar with the kingdoms. I only wanted to show you how the system works.

Five Kingdoms of Life

Classification of Organisms Kingdom Monera: prokaryotes (no nuclei in the cells) include bacteria, cyanobacteria (formerly known as bluegreen algae)

The other four kingdoms have cells with a central nucleus where the genetic material is stored. The nucleus rests within a fluid called cytoplasm that contains various bodies (such as mitochondria and vacuoles). The cell is covered with a cell membrane that controls what chemicals enter and leave the cell.

The next four kingdoms are eukaryotes (having nuclei) Kingdom Protista: microorganisms such as dinofagelata, algae, seaweed, Foraminifera. Kingdom Fungi: mushrooms, molds, yeast, lichens. Kingdom Metaphytae (Plantae): mosses, ferns, trees, flowering plants, salt-marsh grasses. Kingdom Animalia (Metazoa): jellyfish, corals, sponges, sea stars, birds, cats, snakes, etc.

Animalia (Jelly fish)

Protist (Foram) Fungi (mushroom) Plantae (Salt-marsh grass)

Classification by Lifestyle • Plankton: organisms which float in the water and • have no ability to propel themselves against a current -phytoplankton (photosynthetic autotrophs) -zooplankton (heterotrophs) -bacterioplankton (bacteria that float) Nekton: active swimmers and include marine fish, reptiles, mammals, birds and others • Benthon: organisms which live on the bottom (epifauna) or within the bottom sediments (infauna) – Some organisms cross from one lifestyle to another (pelagic early in life and benthonic later)

Charles Darwin’s Theory of Evolution by Natural Selection There are really two parts to this idea. • Evolution is not really a theory but an observation, largely based on the fossil record, that life changes over time. • Natural Selection is the process that Darwin theorized drove evolution. Most biologists believe natural selection is the dominant process. It works as follows: • More offspring are produced than can survive to reproductive age. • Random variations occur in all organisms. Some of these variations are inheritable, that is, they can be passed on to offspring.

• Some inheritable traits are favorable in that they increase the probability that organisms possessing them will survive. • Because bearers of favorable traits are more likely to survive, they are more likely to reproduce and pass on traits. These traits accumulate in the population; they are selected. • The physical and biological environment does the differential selection. Favorable traits are retained because they contribute to the organism’s success in the environment. These traits show up more often in succeeding generations if the environment is constant. If the environment changes, other traits become more favorable and the organisms with those other traits preferentially reproduce in that environment.

How do new traits come about? • Through mutation: inheritable change in an organism’s genes. Most mutations are unfavorable, that is they produce unfavorable traits. Such mutations tend to be eliminated by the environment or other organisms. • Mutations occur randomly, but natural selection is not random. • Natural selection takes huge amounts of time, but there is plenty of time because the Earth is 4. 6 billion years old. • Evolution by natural selection is the accumulation of these beneficial inheritable structural and behavioral trains know as adaptations. • Evolution is the maintenance of life under changing conditions by continuous adaptation of successive generations of species to their environment.

What is a species? • A species is a group of interbreeding organisms that is reproductively isolated from all other forms of life. • Speciation: the process of new species formation. • Physical isolation of a group of organisms is important in speciation. Since the population is small, favorable traits may accumulate rapidly or unfavorable traits may die off to suit a new environment. Generally the smaller the reproducing population, the faster the rate of evolutionary change. • A good example is the one Darwin himself studied: the isolated Galapagos Islands off the west coast of South America. Here are the giant Galapagos tortoises found nowhere else. Darwin theorized that a small population of South American turtles managed to arrive on the islands where the new environment selected traits (like giant size) that are different than the South American traits.

• Divergent evolution: one group radiates into many different species and lifestyles. Example: wolves, foxes, and coyotes have a common ancestor that lived millions of years ago. • Convergent evolution: similar conditions may result in coincidentally similar organisms. Example: porpoises are mammals that originally lived on land had hair, feet with claws, external ears, and mammal-like tails. They moved to the sea and that new environment selected more fish-like traits. • Darwin did not know about DNA or genes so he could only speculate about how new traits form and are passed on.

Evolution Charles Darwin: “I have called this principle, by which each slight variation, if useful is preserved, by the term Natural Selection. ” (The Origin of Species, 1859) Darwin’s theory was based on: Natural Selection heritable variation differential survival Reproduction *but he offers no mechanism

Mechanisms for this theory include: Neo-Darwinism or New Synthesis Is a combination of genetics and Darwinism: postulates that natural selection is the product of mutations in DNA (slow and gradual process)

Symbiosis Close association of two unlike organisms, usually lasting for a long time. Example: Cleaner fish follow sharks closely eating food scraps, dead skin, parasites from the shark’s mouth and sides. In return they get the shark’s protection. Example: Single-celled algae live in the tissues of coral animals. Both organisms get benefits from this association which is called mutualism.

Evolutionary Pathways for Organisms Speciation: is the splitting of a single species, most commonly brought about by populations becoming geographically isolated Divergent evolution: when a single group of organisms splits into two groups and each group evolves in increasingly different directions Convergent evolution: evolutionary change in two or more unrelated organisms that results in the independent development of similar adaptations to similar environmental conditions

GAIA THEORY James E. Lovelock (1972) and Lynn Margulis The scientific hypothesis proposes that the whole Earth behaves like one self-regulating organism wherein all of the geologic, hydrologic, and biologic cycles of the planet mutually self-regulate the conditions on the surface of the Earth.

Gaia Theory • Feedback from biota to biosphere • As biota evolve, so does biosphere “Life and its environment are so closely coupled that evolution concerns Gaia, not the organisms or the environment can be taken separately” (Lovelock, 1993) • Algae and bacteria are key links