Evolution & Changes Over Time UNIT 3

Changes over time, also known as evolution is a process by which modern organisms have descended from ancient organisms.

Evidence of Evolution 1.Fossil record 2.Geographical distribution 3.Homologous structures of living things 4.Similarities in early development

In 1831, Charles Darwin sailed on the HMS Beagle to observe, document and collect specimens around the world.In 1831, Charles Darwin sailed on the HMS Beagle to observe, document and collect specimens around the world. Finches were studied for adaptations in the Galapagos islands.Finches were studied for adaptations in the Galapagos islands.

Darwin’s Voyage

Darwin’s Finches

On this trip, the data derived helped to form Darwin’s Theory of Evolution.On this trip, the data derived helped to form Darwin’s Theory of Evolution. The central ideas of this theory include:The central ideas of this theory include: a)Life changes over time b)Biological diversity of a species leads to “survival of the fittest”

Life changes over time – individual organisms differ and some of this variation is heritableLife changes over time – individual organisms differ and some of this variation is heritable Survival of the Fittest – is the idea that in the struggle for existence, the use of strength, adaptation, survival and reproduction occur over timeSurvival of the Fittest – is the idea that in the struggle for existence, the use of strength, adaptation, survival and reproduction occur over time

Natural Selection – Darwin’s Theory is that the struggle for existence and the survival of the fittest take place without human control or direction. Also, changes in inherited characteristics occur over many generations.Natural Selection – Darwin’s Theory is that the struggle for existence and the survival of the fittest take place without human control or direction. Also, changes in inherited characteristics occur over many generations.

Successful Adaptations – enable organisms to become better suited to survive and reproduce.Successful Adaptations – enable organisms to become better suited to survive and reproduce. –Ex. Quills, better photosynthesis, speed, camouflage

Species today are descended with modifications from ancestral species that lived in the distant past. Diverse species evolve from common ancestors.Species today are descended with modifications from ancestral species that lived in the distant past. Diverse species evolve from common ancestors.

In 1795, James Hutton hypothesized that forces shaped the Earth. Rock layers form slowly over millions of years by some layers being pushed up by forces, buried or forming mountains.In 1795, James Hutton hypothesized that forces shaped the Earth. Rock layers form slowly over millions of years by some layers being pushed up by forces, buried or forming mountains. Charles Lyell’s theory states that past events in terms of processes that are observed which happened millions of years ago are still happening today.Charles Lyell’s theory states that past events in terms of processes that are observed which happened millions of years ago are still happening today.

“The present is the key to the past” is known as uniformatarianism.“The present is the key to the past” is known as uniformatarianism.

The theory that organisms acquired or lost certain traits during their lifetime because of selective use or disuse of organs and then passed these traits on to offspring was developed by Jean-Baptiste Lamarck.The theory that organisms acquired or lost certain traits during their lifetime because of selective use or disuse of organs and then passed these traits on to offspring was developed by Jean-Baptiste Lamarck.

a.Vestigal structures – animal organs that have been reduced in size so that they are vestiges or traces in other species. They serve no useful function in an organism. (ex: Coccyx bone & appendix in humans) b.Homologous structures – structures with different forms in different organisms, but develop from the same embryonic tissue (ex Bird wings & human arms)

In adaptive radiation, fossils indicate that a single species or small group of species evolved through natural selection into diverse forms that live in different ways.In adaptive radiation, fossils indicate that a single species or small group of species evolved through natural selection into diverse forms that live in different ways. An adaptation is any inherited characteristics, physical or behavioral, that increases an organism’s chance of survival.An adaptation is any inherited characteristics, physical or behavioral, that increases an organism’s chance of survival.

Giant Tortoises of the Galapagos Islands

Populations share the same species. New individuals and gene mutations bring alleles into the population. All genotypes in the population must have equal probabilities of survival and reproduction. All phenotypes must have any selective advantage over another.Populations share the same species. New individuals and gene mutations bring alleles into the population. All genotypes in the population must have equal probabilities of survival and reproduction. All phenotypes must have any selective advantage over another.

In small populations, individuals that carry a particular allele may leave more descendants than other individuals simply by chance. This is known as genetic drift.In small populations, individuals that carry a particular allele may leave more descendants than other individuals simply by chance. This is known as genetic drift.

Formation of a new species through natural selection and chance events change alleles frequency and is referred to as speciation.Formation of a new species through natural selection and chance events change alleles frequency and is referred to as speciation.

Directional Selection Individuals at one end of the curve have higher fitness than individuals in the middle or at the other end.Individuals at one end of the curve have higher fitness than individuals in the middle or at the other end. The phenotype of one fails to succeed and others do not. The entire curve movesThe phenotype of one fails to succeed and others do not. The entire curve moves Ex: Darwin’s finches with bigger thicker beaks feed more easily on larger, harder, thicker-shelled seeds (food shortages) text p. 398Ex: Darwin’s finches with bigger thicker beaks feed more easily on larger, harder, thicker-shelled seeds (food shortages) text p. 398

Directional Selection

Stabilizing Selection When individuals near the center of the curve have the higher fitness than the individuals at either end of the curveWhen individuals near the center of the curve have the higher fitness than the individuals at either end of the curve Keeps the curve at its current positionKeeps the curve at its current position Ex: average babies have the best survival and best fitnessEx: average babies have the best survival and best fitness

Stabilizing Selection

Disruptive Selection Upper and lower ends of the curve have higher fitness than individuals near the middle. The curve splits into two.Upper and lower ends of the curve have higher fitness than individuals near the middle. The curve splits into two. Ex: Large and small seeds become more common. Text p. 399Ex: Large and small seeds become more common. Text p. 399

Disruptive Selection

Fossil record – evidence about the history of life on Earth, how it has changed over time, and in a particular order.Fossil record – evidence about the history of life on Earth, how it has changed over time, and in a particular order. Sedimentary rocks – rocks produced by layering of sand, silt, or clay over time.Sedimentary rocks – rocks produced by layering of sand, silt, or clay over time.

Law of superposition – states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest are toward the top.Law of superposition – states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest are toward the top.