Evolution

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Evolution

• How did life begin?

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Age of Earth

• The earth originated 4.6 Billion Years Ago

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Earths Early Atmosphere

• The atmosphere was primitive and made up of
• Methane (CH4), Ammonia (NH3), Hydrogen (H2),
  Water Vapor (H2O), and probably Nitrogen (N2)
• There was no O2

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Life?

• Organic molecules formed from the primitive
  atmosphere (primordial soup) and physical
  processes (volcanoes, lightning, UV radiation),
  and heat bonded amino acids to form proteins.
• RNA stored genetic info and directed protein
  synthesis.
• Pre-Cell early organic molecules enclosed in
  membranes

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Life?

• Because there was no oxygen available, energy
  formed from anaerobic respiration
• There was competition for food, so evolution of
  autotrophs occurred. Autotrophs obtain their
  food from the process of photosynthesis, and this
  process caused an increase of oxygen into the
  atmosphere.

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Earliest Record of Life

• Primitive Cyanobacteria fossils from 3.5 billion
  years ago

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Earliest Record of Life
3.5 Billion Years Old Stromatolite Fossils from
Australia
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Stromatolites

• Limestone deposits from cyanobacteria.

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Stromatolites

• How do we know that stromatolites are formed by
  cyanobacteria???
• They are still around!!!! (Shark Bay, Australia)

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Life!!

• Now aerobic cellular respiration can occur which
  means
• - More ? Energy for Food
• - Greater ? Complexity Among Organisms

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Ozone

• Lightning converted oxygen (O2) to ozone (O3).
  Ozone ? Greenhouse Effect (warming)
• There was a huge explosion of new organisms.

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Overview

• Life evolved from single-celled prokaryotes to
  more complex multi-cellular eukaryotes.

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Evolution

• Change of species over time.
• Pre-Evolution Theory Species are fixed and
  permanent.
• Darwin had trouble with
• this idea! 69 different
• beetle species in 1 hour?

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Evolution Theories

• Lamark (1809) 2 Ideas
• Law of Use and Disuse
• The more an animal uses a particular part of its
  body, the stronger and better developed that part
  becomes.
• Adaptation an inherited trait that improves the
  chances of survival and reproduction of an
  organism

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Lamarck

• Inheritance of Acquired Characteristics
• Lamarck assumed that characteristics an organism
  develops through use and disuses could be passed
  on to its offspring
• Was Lamarck right??

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Lamarcks Example
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Lamarcks Example

• The ancestors of giraffes had much shorter necks
  than present day giraffes and fed on grasses and
  shrubs.
• As food supply decreased, the giraffes stretched
  their necksmaking them longer, and this trait
  was passed on to offspring.

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So what do you think?

• Lamarck was very wrong!!
• Weismann (1870) proved Lamarck wrong
• Cut tails off of mice for 22 generations
• In each generation, the mice were born with tails
  of normal length.
• The acquired characteristic of shortened tails
  was not inherited.

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Charles Darwin (1836)
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Theory of Natural Selection

• Overpopulation more offspring produced than can
  survive
• Competition limited resourcesleads to a fight
  over resources, so some lose and die
• Survival of the Fittest most fit organisms
  survive because not every organism in the
  population is the same (variation)

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Theory of Natural Selection

• Variation organisms are born w/ different
  adaptations (raw material on which natural
  selection acts)caused by changes in DNA
• Gene Pool entire collection of genes among a
  population (the gene pool of a population
  evolves, not individuals)

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Theory of Natural Selection

• Natural Selection nature/environment determines
  which organisms have the best adaptations for
  survival
• Reproduction organisms that survive natural
  selection reproduce and pass on their traits.
  These genes become more common in future
  generations and the species will change over time.

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Theory of Natural Selection

• Speciation (making a new species) if a species
  is split up into 2 different geographical
  locations for a period of time, different
  adaptations may be better for survival. Over
  time one species may diverge enough genetically
  and become 2 different species that cannot breed
  and produce fertile offspring.
• Ex. Galapagos Tortoise

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Speciation

• What about a liger????

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