BIOL 214 TOPIC 2 / CHAPTER 20

Aristotle

• first student of natural history

• said both inanimate objects and living species have fixed characteristics → studying them so we can make a ladder classification of nature

• natural theology

• concepts was merged with bible, “species never change or dissapear or arise”

Natural History

branch of biology that examines the form and variety of organism in their natural environments

Natural Theology

wanted to name and catalog all of God’s creation

Carolus Linnaeus

• Father of modern taxonomy

• established the universally accepted conventions for the naming of organisms

  • important so people w diff languages can understand what species is being talked about

Taxonomy

branch of biology that classifies organisms

Biogeography

• studies of the world distribution of plants and animals

• raised questions

  • if there was a limit to species created by God

  • where did species fit in Scala Natruae

  • how were they spread out if all created in Garden of Eden

Comparative Morphology

• the study of the structural features of organisms to understand evolutionary relationships

  • ie: front legs of pigs, flippers of dolphins, wings of bats, diff in size shape and function, but have similar locations in body, made of bone muscle and skin, and devlop similarly in embryos

  • if limbs were made for different means, why not use different materials to make structures for flying, swimming, and walking?

    • since God’s plan perfect, no need for new plan for every new species (natural theologists)

George-Louis leclerc le Comte de Buffon

• Questioned the existence of body parts with no apparent function (vestigial structures)

• if species perfect, why useless parts

• proposed that animals must have changed since creation, so vestigial structures must have had function in ancestral organisms

Fossils

• remains or traces of ancient organisms preserved in rocks or other materials, providing evidence for the history of life on Earth and evolutionary changes over time

• small and simple ones in deepest layer, gets more complex in above layers (resembled organisms living today)

• fossils found in any particular layer often similar, even if geographically distant

  • some said fossils were remains of extinct organisms, but natrual theology doesn’t allow for this

  • thomas jefferson said remains were extremely rare species

Georges Cuvier

• founder of comparative morphology and paleobiology

• realized layers of fossils represented organisms that lived at successive times in the past

• suggested abrupt changes in rock strata caused dramatic shifts in ancient environments

• catastrophism

Paleobiology

• study of ancient organisms

Catastrophism

• each layer of fossils = remains of organisms that had died in a local catastrophe

• different species then recolonized area

• another catastrophe formed different set of fossils in next, higher layer of rock

Jean Baptiste Lamarck

• wanted a naturalistic explanation for diversity of modern organisms and the animals in fossil record

• “perfecting principle'“: organisms become better suited to their environments, simple → complex

• principle of use and disuse and inheritance of acquired characteristics

Principle of Use and Disuse

• body part grows in prorportion to how much they are used

• ones that aren’t used doesn’t grow and diminishes

  • a body builder and his muscles

Inheritance of Acquired Characteristics

• changes that an organism acquires in its lifetime is passed on to its offspring

  • a body builder’s muscles is passed on to his kid, but not true

4 Large Lamarck Contributions

• all species change through time

• new characteristics are passed from one generation to the next

• organisms change in response to their environments

• hypothesized existence of specific mechanisms that fostered evolutionary change

• these were cornerstones of Darwin’s evolutionary theory

• fostered discussion

James Hutton

• explanation contrasted Cuvier’s catastrophism

  • instead of earth changing sharply in certain events, earth changed slowly time

• gradualism

Gradualism

• slow and continuous physical process over long time made geological features on earth

• ie: movement of water in river slowly erodes land

Charles Lyell

• created Uniformitarianism

• extended Hutton ideas

Uniformitarianism

• geological processes that made the earth’s geology in the past are the same processes that still occur today

• implies that it must have taken millions of years, not a few thousand, to make the landscape the way it is today

Charles Darwin

• traveled world on voyage of beagle, went to south america

• influenced by his teacher Reverend John Henslow, as he arraged for him to go on the trip

• had Lyell’s principles of geology book

Three main observations

• found that fossils resembled organisms inhabiting the same region today

  • darwin thought armadillos might be living descendants of glyptodonts

• animals he encountered in different south american habitats looked like each other but were different from species in europe

  • why did animals that lived in similar environments on separate continents look different?

  • found out that he inherited their similarities from common ancestor

• observed fascinating patterns in species distribution on the Galápagos islands

  • why did they occupy one island custer, why did they look like species from nearest continent?

  • hypothesized that plants and animals of Galápagos islands were descended from south american ancestors, and that each species changed after locating on separate island

Two reflections

• species change through time

• “like begets like”

  • offspring typically resembles parents

  • plant and animal breeders applied this knowledge for lots of years, selective breeding

• read Principles of POpulation by Thomas Malthus

  • applied Malthus’s argument to organisms in nature

  • species produce more offspring than can survive, creates a “struggle for existence” → natural selection

Natural Selection

• individuals in a population compete for limited resources

• hypothesized variations in hereditary traits enabled some individuals to survive and reproduct more than others

• organisms with advantageous traits leave many offspring, whereas those that lacked such traits would die leaving a few if any descendants

  • hereditary traits become more common in the next generation

  • if next generation experienced same process of selection, traits more common in third generation

Darwins observations, hypothesis, and prediction

Observations:

• most organisms produce more than one or two offspring

• populations do not increase in size indefinitely

• food an other resources are limited for most populations

Hypothesis:

• individuals within a population compete for limited resources

Observations:

• Individuals within populations exhibit variability in many characteristics

• Many variations appear to be inherited by subsequent generations

Hypothesis:

• Hereditary characteristics may allow some individuals to survive longer and reproduce more than others

Prediction:

• A population’s characteristics will change over the generations as advantageous, heritable characteristics become more common

Four important distinctions

• darwin provided purely physical, rather than spiritual, explanations for the origins of biological diversity

• darwin recognized that evolutionary change occurs in groups of organisms, rather than individuals

  • some survive and reproduce more successfully than others

• described evolution as a multistep process

  • variations arise within groups, natural selection eliminates unsuccessful variations, and the next generation inherits successful variations

• evolution occurs because some organisms function better than others in a particular environment

Modern Synthesis

• integrates data from biogeography, comparative morphology, comaprative embryology, paleontology, and taxonomy within an evolutionary framework

  • tries to link micro (small scale genetic change) and macro evolution (observed in species and groups)

Observations that support Darwin

• fossil species

  • documents continuity of all species that have ever lived in morphological characteristics

  • provides clear evidence of ongoing change in biological lineages

• historical biogeography

  • species in different areas resemble each other

• comparative morphology

  • homologous traits: characteristics similar in two species because they inherited genetic basis of trait from their common ancestor