EvolutionStandard: SB5d

EQ: How does natural selection lead to a change in a species?

By: Amber Tharpe

Evolution• Change in a species

over time• “descent with

modification”• Theory- subject to

change, but much evidence to support it

• Does not mean humans came from monkeys

• Unites many scientific fields

Lamarck

• Inheritance of acquired traits• An organism could acquire characteristics

during its life and pass them on to offspring• Ex: giraffes stretched their necks to reach

food and passed the long neck trait to their offspring

• Problem- can only pass heritable traits to offspring, not those acquired during life

Darwin

• Naturalist on the Galapagos Islands- observed many species

• Darwinism- evolution by natural selection

• Published Origin of Species in 1859

• Fitness- ability to survive and reproduce better than others

Extinction

• When a species is forever wiped out from existence on earth

• Ex: dinosaurs, dodos, wooly mammoths, saber-toothed tigers

Gradualism

• Theory that biological change results from slow and steady changes over a long period of time

• Small changes add up to large change over time

• Evidence- Intermediate forms are found in the fossil record for some species

• Darwin favored this theory

Punctuated Equilibrium

• Biological change results from a quick, sporadic process over a short period of time

• Mutations of a few genes result in the appearance of a new species

• Evidence- gaps appear in the fossil record

Galapagos Islands

Darwin’s Finches

• Noticed many different types of finches on the Galapagos Islands

• The finches were all related- similar except for their beaks

• Each beak was suited to its diet, the diets varied to the various habitats

• The beaks were adapted to their habitat• Evidence of natural selection

• Geographical Isolation– physical barriers that divide a population into 2 or more groups

• Speciation– the rise of 2 or more species from 1 existing species

• Lyell– Tectonic plate shifting– Land was once all connected as one continent,

Pangea• Wallace

– Came up with the theory of natural selection at the same time as Darwin

• Mendel- late 1800’s– Genetics and heredity support theory of natural

selection– Genes provided the missing link for how traits

could pass from parent to offspring

Natural Selection

• Aka. “Survival of the fittest”• Individuals with more favorable

characteristics survive and reproduce better than others

• Mechanism that causes evolution• Acts on phenotypes (physical

traits), not genotypes

Steps of Natural Selection

1.Variation2.Overproduction3.Adaptation4.Descent with Modification

• Variation– Natural differences between individuals of a

species• Overproduction

– More offspring are produced than can survive– There are not enough resources, so there is

competition for them• Adaptation

– A certain feature that allows an individual to survive better and reproduce in its environment, so it is “naturally selected”

• Descent with modification–When individuals with this adaptation survive and reproduce, they pass the genes for this trait to their offspring

–The trait becomes more common in the population as long as it provides a benefit

Artificial Selection

• Breeding• When humans decide what

traits are favorable and select for them

• Ex: toy, miniature, and teacup dogs

Fossils• Fossils provide evidence of organisms that

once lived• Ex: Skeletons, bone fragments, footprints,

ect• Form in wetlands or on the floor of bodies

of water• Show changes in organisms over time

– evidence of evolution• Paleontology- the study of fossils

Dating Fossils

• Relative dating-– Deeper layers of rock are older, while those

closer to the surface are younger– We use the placement of fossils in the layers

to determine the approximate age the organism lived

• Radiometric dating-– Use half-lives of radioactive isotopes found in

the living organisms

Biogeography• The distribution of

species on earth• Ex: don’t find the same

exact species on an island and the mainland

• Provides evidence for evolution

• Characteristics of organisms are well-suited to their environment

Embryology

• The structure of animals before birth• Many organisms are similar in appearance

as embryos but are significantly different as adults

• The sooner a characteristic appears in development, the older the trait is

• The similarities provide evidence for evolution

Comparative Anatomy or Morphology

• Homologous structures– Similar body parts that come from a common

ancestor– Ex: fins of whales, wings of bats, and arms of

humans• Analogous structures

– Serve the same purpose, but not from a common ancestor

– Ex: wings of insects, bats, and birds

• Convergent evolution–Unrelated species become similar

due to a similar environment–Ex: analogous structures

• Divergent evolution–Related organisms become more

and more different due to isolation–Ex: speciation

Homologous Structures

Analogous Structures

Comparative Anatomy or Morphology

• Vestigial Organs–Structures that have no use–Remnants of structures that had a function in an earlier ancestor

–Ex: wings on flightless birds, appendix in humans

Biochemistry and Molecular Biology

• Comparing DNA or proteins–Same 4 nucleotides make up DNA for

all living things–Same 20 amino acids make up

proteins for all living things–The more similar DNA or proteins, the

more closely related 2 organisms are

Phylogenic Trees

• Family trees that show evolutionary relationships–Can be made by examining evidence of evolution

Origins of Life

• Life on earth began 4.5 billion years ago– Water was present and prokaryotes were the

first organisms to live– Eukaryotes came from small prokaryotes

living symbiotically in larger prokaryotes • endosymbiosis- mitochondria and chloroplasts

were formed this way– Sexual reproduction gave greater diversity

Geologic Time Scale• Precambrian- bacteria lived• Cambrian explosion- time when a huge

diversity of animal species evolved• Paleozoic Era- invertebrates, reptiles, and

seed plants lived• Mesozoic Era- dinosaurs, birds, flowering

plants lived• Cenozoic Era- Mammals and humans

lived

Geologic Time Scale

• Units of time from largest to smallest– Era– Period– Epoch

Coevolution

•When a species evolves in response to changes in another species

•Ex: plants and insects

Biological Resistance

• Living organisms over time become resistant to substances made to kill them

• Ex: antibiotics, pesticides, herbicides, ect

• Due to natural selection