Evolution Evidence and Theory Chapter 14 Honors Biology

Early Biological Though �Heavily influenced by theology �All organisms were created simultaneously �Each distinct life-form was permanently fixed and did not change over time

Evolution- Is it true? � A genetic change within a population over time! � Population- interbreeding singlespecies group

Fossils. Documentation �Fossil - trace of a long-dead organism. �Sedimentary rock - formed by dust, sand, or mud deposited by wind or water over dead organism �Formed by hard body parts of an organism—shell, bones, teeth, or woody stems �Hard minerals replace the tissue of the organism leaving rocklike

Sedimentary Rock

Fossils �Mold – imprint in rock in the shape of an organism �limestone �Cast – forms when molds are filled with hard minerals Mold Cast

Limestone �Limestone – most abundant , non-classic sedimentary rocks. �Limestone is produced from the mineral calcite (calcium carbonate) and sediment. �Chalk is another type of limestone that is made up of very small single-celled organisms.

Robert Hooke 1635 -1703 �He concluded that fossils are remains of plants and animals �He mostly studied “petrified wood” with the aid of the microscope �He hypothesized that living organisms had somehow been turned to rock

Petrified Wood that has turned to stone!

Non-evolutionary Explanations �Catastrophism �Georges Cuvier (1769 -1832) �High numbers of species were created originally �Series of catastrophes produced rock layers �destroyed many species, preserving some as fossils �Modern day species are the

Uniformitarianism �James Hutton (1726 -1797) and Charles Lyell (1797 -1875) �Developed theory of uniformitarianism �Geologic change resulted from slow, continuous actions similar to those at work today

Distribution of Fossils �Nicolaus Steno (1638 -1686) �“law of superpositon” – states that the top layers of stratum contain the youngest fossils while the lower ones are older �Determine the “relative age” of a fossil �“absolute age”- age in years determined by radiological evidence

Succession of Forms �Mass extinctions – brief periods during which large numbers of species disappears. �Resulted from drastic changes in the environment, volcanic activity or collisions with asteroids (may have blocked sunlight for long periods of time and decreased temp. )

Biogeography �Biogeography – is the study of the geographical distribution of fossils and of living organisms. �A comparison of fossil types with types of living organisms in the same geographic area �shows that new organisms arise in areas where similar forms already lived. �Ex: armadillos in North & South America where glyptodonts lived in the past.

Armadillos

Glyptodonts

Scaphognathus crassirostris Lab Fossil

Theories of Evolution �I. Lamarck’s Explanation: �He hypothesized that acquired traits were passed on to offspring. �Proposed that similar species descended from a common ancestor (fossil records)

Acquired Trait �It’s not determined by genes! �Occurs during an organism’s lifetime �result of the organism’s experience or behavior. �Ex: 1. Muscles on a body builder � 2. Giraffe’s necks did not get longer by trying harder and harder to reach tall trees- Genetic

Beginning of Modern Evolutionary Theory �II. Charles Darwin (1809 -1882) & Alfred Wallace (1823 -1913) �Darwin & Wallace announced their hypotheses at the same time �Darwin’s name became more associated with evolution The Origin of Species published

Darwin’s Voyage on the Beagle �Sailed in 1831 for five years �Collected specimens and kept careful records of his observations �Sailed to South America (Galapagos Islands) and the South Pacific

Voyage of the Beagle

Darwin’s Findings �Collected 13 similar but separate species of finches. �Each finch species had a distinctive bill for specialized food source. �Implied that the finches shared a recent common ancestor

Darwin’s Finches

Darwin’s Findings

Darwin’s Theories �TWO THEORIES; � 1. DESCENT WITH MODIFICATION – The newer forms appearing in the fossil record are actually the modified descendants of older species �Organisms similar to each other- common ancestor �Organisms that are dissimilar -share a more remote ancestor

2. Modification by Natural Selection � MODIFICATION BY NATURAL SELECTION – states HOW evolution occurs. �Organisms best suited to their environment reproduces more successfully than other organisms Leaf tailed gecko

Postulate- something taken as self-e Based on 4 postulates � 1. Individual members of a population differ �Variations arise purely by chance resulting from random mutations in DNA � 2. Variations are passed from parent to offspring � 3. Some individuals in a population survive and reproduce successfully but others do not � 4. Individuals with advantageous traits survive longest and leave the most

Adaptation- Adaptive advantage �A population of organisms adapt to their environment �# of genes for favorable traits increases �Fitness- a single genetic organism’s contribution to the next generation’s survival �A well adapted organism will reproduce successfully and have a high fitness

High Fitness? Low Fitness?