Descent with Modification A Darwinian View of Life

Descent with Modification: A Darwinian View of Life

3 key observations about life 1. 2. 3. Striking ways organisms are suited to their environment Unity of living things(so many common features) Rich diversity of life

EVOLUTION DESCENT WITH MODIFICATION

EVOLUTION A CHANGE in the GENETIC COMPOSITION of a POPULATION from GENERATION to GENERATION

EVOLUTION � 1. CAN BE VIEWED IN 2 WAYS A PATTERN � 2. OBSERVATIONS FROM NATURAL WORLD A PROCESS � MECHANISMS THAT PRODUCED THE OBSERVED PATTERNS

ARISTOTLE (384 – 322 BCE) � � DID NOT BELIEVE ORGANISMS CHANGED OVER TIME (some Greeks did) Viewed organisms as fixed: could be arranged on ladder from least complex most complex

SCALAE NATURAE

CAROLUS LINNAEUS (1701 – 1778) � � DEVELOPED BINOMIAL NOMENCLATURE WITH A “NESTED” CLASSIFICATION SYSTEM

LINNAEUS CLASSIFICATION SYSTEM

PALEONTOLOGY STUDY OF FOSSILS � GEORGES CUVIER (1769 – 1832) � �OLDER THE STRATUM OF SEDEMENTARY ROCK THE OLDER & MORE DISSIMILAR THE FOSSILS WERE TO CURRENT LIFE �NEW SPECIES APPEARED, SOME DISAPPEARED

GEORGES CUVIER CATASTOPHISM: EVENTS IN THE PAST OCCURRED SUDDENLY & WERE CAUSED BY DIFFERENT MECHANISMS THAN SEEN NOW

JAMES HUTTON (1726 – 1797) Scottish Geologist � Explain geologic features by gradual mechanisms still going on now �

CHARLES LYELL (1797 – 1875) � Principle of Uniformitarianism �Mechanisms of change are constant over time

Hutton & Lyell’s ideas influenced Darwin � Both indicated Earth had to be much older than previously believed � Darwin reasoned: slow & subtle processes could produce biological changes �

Lamarck’s Hypothesis of Evolution � 1 st to propose mechanism of evolution �Parts of body used the most become larger, stronger; parts not used deteriorate �Inheritance of Acquired Traits

What does “Inheritance of Acquired Characteristics” Mean? � Example: A population of giraffes all had short necks and were able to reach their food. However, when they were forced to move to an area with taller trees, they could no longer reach their food. So they stretched and stretched until they could reach. Then when Mr. & Mrs. Giraffe had babies, their babies had long necks because their parents had acquired long necks.

Just because… � Louis the Short-Necked Giraffe

LAMARCK (1744 – 1829) � EVOLUTION HAPPENS BECAUSE ORGANISMS INATELY WANT TO BECOME MORE COMPLEX

CHARLES DARWIN (1809 -1882)

VOYAGE of the BEAGLE 1831 - 1836

Darwin’s Observations Plants & animals in temperate zones of SA closely resembled plants & animals of temperate regions of Europe � Fossils in SA resembled living organisms in SA �

GALPÁGOS

Darwin’s Observations: Descent with Modification � Took note of many adaptations saw adaptations & the origin of a new species as closely related processes

Darwin’s Finches � � 14 different species each clearly adapted to a specific niche all similar to finches on mainland SA (common ancestor)

Darwin’s Theory � Proposed that natural selection over long periods of time could cause an ancestral species to give rise to 2 or more descendant species

� Natural Selection: a process in which individuals with certain inherited traits tend to survive & reproduce at higher rates than other individuals without those traits

The Origin of the Species by Means of Natural Selection � Darwin provided massive amounts of evidence that descent with modification by natural selection explains : � Unity of Life � Diversity of Life � Match between Organisms & their Environment

NATURAL SELECTION � Differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. Evolution occurs when this causes changes in relative frequencies of alleles in the gene pool. ARTIFICIAL SELECTION � Selecting and breeding individuals that possess desired traits

NATURAL SELECTION ARTIFICIAL SELECTION

Darwin’s Reasoning OBSERVATION 1. Population sizes would increase exponentially if all individuals were successful in reproducing OBSERVATION 2. Populations tend to remain stable in size (other than seasonal fluctuations)

Darwin’s Reasoning OBSERVATION 3. Resources are limited INFERENCE 1. overpopulation leads to competition, those with traits that will help them survive reproduce more passing along favorable traits

Darwin’s Reasoning OBSERVATIONS 4. There are variations of traits in populations 5. Variation is mostly heritable INFERENCES 1. 2. Individual with variations that are favorable will leave more offspring than one without those traits Unequal ability to survive and reproduce leads to a change in a population

SURVIVAL of the FITTEST

Over time natural selection increases the match between organisms & their environment

When the environment changes natural selection may result in adaptations that give rise to a new species

Natural Selection in Action � Natural selection can happen rapidly and observed directly � guppies, � Drug-Resistant HIV Also observed by researchers in the fields of anatomy, embryology, molecular biology, biogeography, and paleontology � homologous and vestigial structures � molecular homologies: same DNA, RNA; universal genetic code � biogeographically distribution of organism � comparative data from biochem, molecular biology and cell biology support the oldest known fossils are prokaryotes

HOMOLOGY � SIMILARITY RESULTING FROM COMMON ANCESTORS

Homologous Structures: Embryology � Similarities in early stages of development suggest common ancestry �At some point in development all vertebrates have a tail

VESTIGIAL STRUCTURES � REMNANTS OF FEATURES THAT WERE IMPORTANT IN EVOLUTIONARY ANCESTOR

Molecular Homologies � � � All life forms use DNA & RNA Genetic code is universal Some human genes code for exact same protein as bacterial gene �+/- � have same function Some organisms carry “vestigial genes”

Evolutionary Tree � Can organize organisms with shared characteristics in nested groups �Deepest layer all living things share �Each successive smaller group have their own unique homologies

Evolutionary Trees � are hypotheses that summarize our current understanding of patterns of descent

Convergent Evolution � The independent evolution of similar features in different lineages

Analogous Features � are seen in species that share similar structures but not common ancestry

The Fossil Record Shows: 1. 2. 3. past organisms differ from current ones many species have become extinct the evolutionary changes that have occurred in various groups of organisms

BIOGEOGRAPHY � � The GEOGRAPHIC DISTRIBUTION of ORGANISMS Influenced by: �Continental Drift 250 million yrs ago all land masses joined Pangea 200 million yrs ago split began 20 million yrs ago looked close to what we have today

Continental Drift � Understanding continental drift scientists look for fossil evidence explained by the movement of land masses

Summary: 4 Types of Evidences for Evolution 1. Direct Observations 1. 2. Anatomical Similarities 1. 2. 3. 4. Effect of invasive species Drug-resistance in bacteria Homologous & Vestigial Structures Universal Genetic Code Fossils Biogeography