Evolution of Populations Chapter 16 (M)

Evolution  a continuing process of change in a population of organisms over long periods of time

History 1700s  Scientists believed that “Species are Fixed” and do not change Mid 1700s  fossil records lead Georges Buffon to say  Earth is older than 6000years  Different species arose from variation from a common ancestor 1800s  Lamarck explained fossil records & species diversity

Lamarck Proposed the theory of “Inheritance of Acquired Characteristics”  body changes developed during an organisms life time could be passed on to the offspring

Short neck  ate up grass  had to stretch neck to reach trees

Lamarck Acquired characteristics would have to modify DNA to be inherited  no evidence of this Lamarck’s theory was rejected Set the stage for Darwin

Variation in the population  long & short necks Long necked survived  reproduced  population was gradually changed to long necked animals

Darwin( ) Started his voyages at the age of 22 on the HMS Beagle Was responsible for collecting specimens of fossils He was aware of geological formations of land masses  could explain fossils of snails from mountains Studied his collections for the next 22 years

Darwin’s Key Observations 1. Fossils & fossil records show that organisms  simpler  complex 2. Overproduction of offspring 3. Limited supply of resources in an environment 4. Survival in a limited environment depends in part on features inherited from parents

Information that influenced Darwin Charles Lyell  geologist proposed that the Earth was very old and had slowly been changing for millions of years Thomas Malthus  economist  social problems as a result of the exponential growth of the human population Artificial selection by breeders

Darwin Concluded 1. Descent with Modification 2. Natural Selection

Descent with Modification All present day organisms are related through descent from unknown ancestors in the past. These descendants of earliest organisms spread into different habitats  adapted to diverse ways of life

Natural Selection Individuals whose inherited characteristics adapt them best to their environment are most likely to survive and reproduce Basic Mechanism of Evolution  Natural Selection

Natural Selection Occurs over a vast period of time Individuals undergo selection, but do not evolve  Populations Evolve

Evidence of Evolution Section 16.4(M)

Evidence 1. Fossil Records 2. Comparative Anatomy 3. Embryonic Structures 4. DNA Homology

Fossils Remains, traces or imprints of an organism preserved in the earth’s crust  Imprint  Mold  Cast  Petrified

Fossil Records 1. Fossils & the order in which they appear in layers of rocks 2. Fossil records show that animals & plants have appeared in a historical sequence, fossils found in rocks of different ages differ because life on Earth has changed through time

Each Layer represents a particular time period

Comparative Anatomy The comparison of body structures in different species Homologous Structures Analogous Structures Vestigial Structures Ex: common descent  evident in anatomical similarities between species in the same taxonomic group

Homologous Structures Structures that are similar & have been derived from a common ancestor, but have been adapted to different functions. ex: humans, cats, whales, bats  all mammals Whales’ flipper does not have the same function as a bat’s wing

Homologous Structures

Analogous Structures Body parts similar in function but have different structures Ex: wings of insects and birds

Vestigial Structures Body parts reduced in size & appear to serve no function

Embryonic Structures Embryos of closely related organisms often have similar stages in development

DNA Homology Comparison of genes and proteins shows the relationships between species

Darwin’s Natural Selection : A Mechanism of Evolution

Natural Selection Regional and timely Adapts organisms to their local environment Environmental factors vary from place to place & time to time  adaptation in one situation may be useless in another Example: Biston betularia  peppered moth

Peppered Moth England  two varieties  dark & light 1850  almost all were light  industrial revolution  pollution  tree trunks turned black  light moths became easy prey Dark survived & reproduced End of century  almost all were dark

Biston betularia : peppered moth

Populations A group of individuals of the same species living in the same place at the same time Mainland animal species colonizes a chain of distant and isolated islands  separate population. These populations adapt to their local environments. Over time, the isolated populations would become more and more different. And over many generations, the populations could become different enough to be separate species.

Darwin’s Finches  adapted to different food sources  beak Structures

Variation Differences among members of the same Species

Adaptation Inherited trait that Improves the Chances Of Survival & Reproduction 1. Structural  mimicry  organism copies the appearance of another species 2. Physiological  changes in the organisms metabolic process  penicillin  drug resistant bacteria 3. Behavioral  inherited behavior pattern that allows organism to survive

Adaptation- Mimicry Monarch  tastes bitter  birds avoid them because they get sick Viceroy(extra black lines on wings)  not bitter, look & act like Monarchs  birds avoid them

Adaptation: Camouflage Protective adaptation that allows an organism to blend into its surroundings The better the camouflage, the more likely it is for the organism to survive and reproduce

Adaptation: Camouflage

Artificial Selection Selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value.

From Wild Mustard to our Table

Pesticides- Natural Selection in Action Spraying crops  kill insect pests  favored the reproduction of insects with inherited resistance to the poisons