CHANGE OVER TIME and CLASSIFICATION

Darwin’s Theory Of Evolution

Evolution The process of change over time Photo by Vector Open Stock/ CC BY

In Darwin’s travels aboard the HMS Beagle, which began in 1831, Charles Darwin made three important observations: The world includes a tremendous diversity of living things throughout a wide range of habitats Animal species, like those in the Galapagos Islands, that are related, can have different characteristics or occupy different habitats in the same area. Fossils — preserved remains of ancient organisms, resembled

Darwin’s observations led him to develop the scientific theory of evolution which explains how modern organisms evolved over long periods of time by natural selection. Adaptation — a trait that helps an organism survive and reproduce.

Natural selection — process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species. Photo by Martinowksy / CC BY-SA

Factors that affect process of natural selection: • Overproduction — species produce more offspring than one can survive (insects, fish) • Variations — difference between individuals • Competition — resources are limited, species must compete to survive

Evolution Of Populations Photo by Paulmaz  / CC BY

Genetically speaking, evolution is a change in the frequency of alleles in a population over time. Three sources of genetic variations: Mutations — charge in genetic material of cell Genetic Recombination — during sexual reproduction each chromosome in a pair moves independently during meiosis — in humans this can produce over 8,000,000,000 gene combinations Lateral gene transfer — passing of genes from one organism to another (not including offspring) Gene pool — consists of all genes, including all the different alleles, that are present in a population

Hardy — Weinberg principle States that allele frequencies will remain constant or have genetic equilibrium, unless factors cause those frequencies to change. Hardy–Weinberg proportions for two alleles: the horizontal axis shows the two allele frequencies p and q and the vertical axis shows the expected genotype frequencies. Each line shows one of the three possible genotypes. Photo by Johnuniq / CC BY-SA

The Hardy—Weinberg principle holds under these five conditions: 1 The Hardy—Weinberg principle holds under these five conditions: 1. random mating 2. very large population 3. no movement in or out of population 4. no mutations 5. no natural selection

Reproductive isolation When two populations no longer inter breed, can cause evolution of two separate species. This can be caused by behavioral isolation, geographic isolation and temporal isolation. Photo by JJ Harrison / CC BY-SA

The Fossil Record

Paleontologists — scientist who studies fossils or the preserved remains or traces of organisms that have lived in the past. Fossil record — collections of fossils organized to provide evidence about history of life on Earth, including how organisms have changed over time.

The formation of fossils are rare but can occur by: Petrified Fossils Molds and Casts Preserved Remains — remains are buried in sediment then change to rock over time – now called petrified fossil — hollow space in sediment in the shape of an organism is called a mold; when a mold becomes filled with hardened minerals it becomes a cast. —quickly buried organisms are preserved by ice, volcanic ash or clay before they begin to decay.

Relative Dating Vs. Radioactive Dating Paleontologists use the geological time scale, or a “Calendar” of Earth’s history, to represent evolutionary time. After Precambrian Time, the geological time scale is divided into eras (Paleozoic, Mesozoic and Cenozoic) and those eras are subdivided into periods, which range in length from tens of millions of years to less than two million years. Age of fossils is determined by comparing its placement with that of fossils in other layers of rock. Involves measuring the amounts of radioactive isotopes in a sample to determine its actual age

Classification

In the 1730’s, Carolus Linnaeus, a Swedish botonist, developed a two- word naming system called binomial nomenclature — first part of name is genus with second part of name referring to species.

The 1735 Classification of Animals Linnaeus also developed a classification system which included hierarchal taxa: The 1735 Classification of Animals

Sometimes classification keys are used to identify organism by traits that are visible, however scientists today now look at how closely members of groups are related. Phylogeny — study of how living and extinct organisms are related to one another Clade — group of species that includes a single common ancestor and all descendants of that ancestor.

Cladogram — diagram that links groups of organisms by showing how evolutionary lines, or lineages branched off from common ancestors. Derived Character — trait that arose in the most recent common ancestor of a particular lineage and passed to its decendants.

Domains And Kingdoms

Organisms are placed into domains and kingdoms based on their cell type, their ability to make food, and the number of cells that make up their bodies. Photo by Vojtěch Dostál / CC BY-SA

CLASSIFICATION OF LIVING THINGS DOMAIN Bacteria Archaea Eukarya KINGDOM Eubacteria Archae- bacteria Protista Fungi Plantae Animalia CELL TYPE Prokaryote Eukaryote ( lacks a nucleus ) CELL STRUCTURES Cell walls with Peptide-glycan Cell walls without Some cell walls of cellulose Cell walls of chitin of cellulose   No cell walls or chloro-plasts Some chloro- plasts Chloro-plasts

# OF CELLS Unicellular Most unicel- lular Most multicel- Multicel- Some colonial Some uni Some green Algae uni Some multi MODE OF NUTRITION Autotroph or Heterotroph Auto-troph or Hetero-troph Autotroph EXAMPLES E. Coli Halophiles Amoeba, Slime molds Mushroom Yeasts Mosses, ferns, flowering plants Sponges, norms, insects, fish, mammals