Evolution

Evolution

  • What is evolution?
  • Evolution is the biological change process by which descendants come to differ from their ancestors.
  • What are species?
  • A species is a group of organisms that can reproduce and have fertile offspring.
  • There were many important naturalists in the 18th century
  • Linnaeus (1735) classification system for kingdom to species
  • Buffon: species shared ancestors rather than arising separately
  • E-Darwin: more-complex forms developed from less-complex forms
  • Lamarck: environmental change leads to use or discuss of a structure
  • Who is Darwin?
  • Darwin was a naturalists
  • He traveled on the HMS Beagle surveying and charting the land for 5 years (1831). He also collected specimens and made a lot of observations along the way.
  • Darwin observed differences among island species
  • Variation is a difference in a physical trait within the same group.
  • Galapagos tortoises that live in areas with tall plants have long necks and legs.
  • And tortoises that lived in wet areas rich in mosses had short neck and legs.
  • Galapagos finches that live in areas with hard-shelled buts have strong beaks
  • And finch with more delicate beaks were found in areas where insects and fruit were widely available.
  • Adaption
  • An adaptation is a feature that allows an organism to survive better in its environment.
  • Species are able to adapt to their environment.
  • Adaption can lead to genetic change in a population.
  • Darwin observed fossil and geologic evidence supporting an ancient Earth.
  • Darwin found fossils of extinct animals that resemble modern animals.
  • Darwin found fossil shells high up in the Andes mountains
  • Andes Mountain
  • The Andes is the longest mountain range on land. It was formed along the western margin of South America, where two tectonic plates (rocky plates that make up the Earth’s crust) collided. The mountains are still rising by about 10cm (4in) every century. 2.5 miles high, 120 miles long, 430 miles wide.
  • Darwin’s Voyage
  • During his voyage Darwin experienced an earthquake
  • He saw land move from underwater to above sea level
  • Darwin extended his observations to the evolution of organisms.
  • Geological processes can add up to great changes over time.
  • Concluded that the Earth must be old & that slow, gradual changes resulted in the evolution of organisms over time.
  • Several key insights led to Darwin’s idea for natural selection
  • Darwin noticed a lot of variation in domesticated plants and animals
  • Artificial selection: the process by which humans select traits through breeding.
  • Natural selection: is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than other individuals.
  • Heritability is the ability of a trait to be passed down.
  • There is a struggle for survival due to overpopulation and limited resources
  • Darwin proposed that adaptations arose over many generations.
  • Natural selection explains how evolution can occur.
  • Four main principles of natural selection:
  1. Variation: different physical traits, needed for evolution to take place.
  2. Overproduction: having a lot of offspring causing competition.
  3. Adaption: one variation has to be better than the other
  4. Descent with modification: over time the best trait will dominate.
  • Natural selection acts on existing variation.
  • Fitness: the measure of survival ability and ability to produce more offspring.
  • Natural selection can act only on traits (phenotype) that already exist
  • Structure take on new function in addition to their original function. Panda wrist acts as a thumb.
  • Natural selection acts on distributions of traits.
  • A normal distribution graph is a bell-shaped curve. This tells us that the trait is not undergoing natural selection.
  • Highest frequency near mean value.
  • Frequencies decrease toward each extreme value.
  • Natural selection can change the distribution of a trait in one of three ways.
  • Microevolution is evolution within a single population on a smaller scale.
  • Observable change in the allele frequencies.
  • Can result from natural selection.
  • Natural selection can take one of three parts.
  1. Directional selection
    • One extreme phenotype is preferred.
    • ex: bacteria and antibiotic drugs.
  • Directional selection: the type of selection works to select the extreme of one trait
  1. Stabilizing selection
    • The intermediate phenotype is preferred
    • ex: human baby weight
  2. Disruptive selection: both extreme phenotypes is preferred
    • ex: black and brown mice of Arizona
  • Sexual selection occurs when certain traits increase mating success.
  • How sexual selection works: female choose a mate due to their higher cost of reproducing offspring.
  • Males produce any sperm continuously
  • Females are more limited in potential offspring each cycle and they need to be choosy.
  • There are two types of sexual selection
  • Intrasexual selection: competition among males for mates
  • Intersexual selection: males display certain traits to attract females.
  • Intra: inside/ same
  • Inter: between
  • Evidence for evolution in Darwin’s time came from several sources
  1. Fossils provide evidence of evolution.
  • Fossils: we can see how organism have changed over time, old layers of rock are more primitive than those in the upper layers.
  • The study of geography provides evidence of evolution.
  1. Biogeography: island species most closely resemble nearest mainland species.
  • Populations can show variation from one island to another.
  • Embryology provides evidence of evolution.
  1. Embryology: similar embryos become diverse organisms, tells us they had a common ancestor.
  • Identical larvae, different adult body forms.
  1. Anatomy studies body structures of living things. Anatomy provides evidence of evolution.
  • Homologous structures: similar in structure but different in function.
  • Evidence of a common ancestor.
  • The study of anatomy provides evidence of evolution
  • Analogous structures: different structure with similar function.
  • ex: fly wing and bat wing
  • Shows no evidence of a common ancestor.
  • Vestigial structures: remnants of organs or structures that had a function in an early ancestor.
  • Molecular evidence support evolution.
  1. DNA: two closely related organisms will have similar DNA sequences.
  • New species can arise when populations are isolated.
  • The isolation of populations can lead to speciation.
  • Populations become isolated when there is no gene flow
  • Genetic differences can add up over generations.
  • Speciation is the rise of two or more species from one existing species due to no gene flow between populations
  • Reproductive isolation can occur between isolated populations.
  • members of different populations cannot mate successfully
  • final step to becoming separate species
  • Populations can become isolated in several ways
  1. behavioral isolation
  • difference in courtship or mating behaviors
  1. geographic isolation
  • physical barriers divide populations (mountains, rivers, oceans.)
  1. temporal isolation
  • temporal barriers can cause isolation
  • different timing of reproductive periods prevents mating