EvolutionLab 13

Theory of Evolution

Describes: Genetic change in populations

Evidences of Evolution

Evolution: process by which life has changed through time.

There are different types of data that support the theory of evolution:

Some are: 1. fossil record2. comparative anatomy 3. molecular differences

Fossils

Remains or evidence of some organism that lived long ago.

Can be used to trace the history of life on earth

Comparative Study

Comparatived study of the anatomy of modern groups of organisms has shown that each group has strucutures of similar construction

Called Homologous structures Example: all vertebrate animals have

essentially same type of skeleton. Homologous structures are theorized to signify

relatedness through evolution.

Molecular differences

Living organisms use the same basic molecules

Including ATP, DNA, proteins

Evidence from the fossil Record

Geologic Timescale Developed by both geologists and

paleontologistsDepicts history of life based on the

fossil record (page 230)

Divisions of the Timescale

Timescale divides the proposed history of Earth into eras, then periods, and then epochs.

4 eras span the greatest amounts of time, and the epochs are the shortest time frames.

Note

Only the periods of the Cenozoic Era are divided into epochs

More attention is given to the evolution of primates and flowering plants than to the earlier evolving organisms

Partner up and answer questionsPage 315

Dating within the timescale

Timescale provides both relative dates and absolute dates.

Ex: relative time: “flowering plants evolved during the Jurassic period”

Flowering plants evolved earlier or later than groups in other periods

Ex: absolute time: using dates that ar in millions of years (mya)

Limitations of the timescale

Appears evolution occurred from cell to human

Not the case Prokaryotes – bacteria and Achaea – never

declined and are still most abundant and successful organisms on earth.

Constitute 90% of total weight of living things

Extinction (still in limitations of time scale)

Timescale lists mass extinctions Does not tell when specific groups became

extinct. Extinction – total disappearance of a species or a

higher group Mass extinction – occurs when a large number of

species disappear in a few million years or less. For lack of space: geologic timescale cant depict

in detail what happened to members of every group mentioned. See figure 23.1

Observation of Fossils

Page 232: Viewing fossils

Evidence of Comparative Anatomy

Organisms or parts of organisms are said to be “homologous” if they exhibit similar basic structures and embryonic origins.

If similar in function only – said to be “analogous”

Only homologous structures indicate an evolutionary relationship and are used to classify organisms.

Comparison of Adult Vertebrate Forelimbs

Page 234 The limbs of vertebrates are homologous

structures. Homologous structures share basic pattern,

although there may be specific differences. Descent from a common ancestor

Analyze bones and fill in Table 23.5 on page 234

Vertebrate forelimbs

Comparison of Chimpanzee & Human Skeletons

Bones are closely relatedExamine the skeletons on page 236They are adapted to different ways

of lifeTrees vs. us; herbivores vs

omnivores

Page 237: Analyze a human and a chimp

Answer questions – work together if wish

Page 238: Skull analysis

Answer questions regarding facial features (page 238)

Molecular Evidence

Almost all living organisms use the same basic biochemical molecules

DNA, ATP, Proteins (same amino acids)

Protein differences

Protein Clock HypothesisNumber of amino acid changes

between organisms is proportional to the length of time since the two organisms began evolving separately from a common ancestor.

Protein Similarities

Immune system makes antibodies (proteins)

React with foreign proteins – AntigensAntigen-antibody reactions are specific