Chapter 25 The History of Life on Earth

1
Chapter 25The History of Life on Earth

• Barbara Musolf
• Clayton State University
• Admin Building A 16-C
• 678-466-4851

2
Objectives

• Conditions that led to origin of life on earth
• The history of life as seen in fossils
• Key events include origin of single-cellular and
  multi-cellular organisms and the development of
  terrestrial life
• The effects of continental drift, mass
  extinctions, and adaptive radiation on groups of
  animals
• Developmental genes can radically change body
  forms
• Understand why evolution is NOT goal oriented.

3
Early earth

• Abiotic synthesis of amino acids and nucleotides
• Formation of macrocmolecules (proteins and
  nucleic acids)
• Packaging these molecules into protobionts
• Origin of self replicating molecules that led to
  inheritance

4
Synthesis of organic compounds

• Oparin-Haldane hypothesisEarly earth was a
  reducing atmosphere that led to synthesis
• Miller and Urey tested the hypothesis which
  yielded amino acids
• Demonstrated that abiotic synthesis was possible
• Analysis of meteorites show presence of AAs
• Synthesis of macromolecules may have been
  initiated by formation of AA polymers

5
Protobionts

• Protobionts are abiotically created molecules
  surrounded by a membrane.
• They can engage in simple reproduction and
  metabolism
• The can maintain an internal environment
  different than the external environment.
• Liposomes can spontaneously organize in water
  from lipids and organic molecules

6
Self replicating RNA

• RNA catalysts are called ribozymes
• Protobionts with RNA were more successful
• The development of DNA provided a more stable
  molecule for genetic information

7
Key events in earths history
8
The First Eukaryote
9
The First Eukaryote
10
Origin of multicellularity

• First evidence of multicellular organisms (algae)
  1.2 billion years
• The fossil record indicates that the first major
  diversification of multicellularity was after a
  thaw 565 million years
• Ediacaran biota
• The Cambrian explosion

11
Colonization of land 500 mya

• Adaptations developed to live on land
• Plants produced waterproof coating and a vascular
  system for internal transport
• Early plants had no roots or leaves
• Fungi followed plants
• Arthropods are the most abundant land animals
• Tetrapods arrived 365mya
• Our species arrived 195,000 years ago

12
Rise and fall of organisms

• Continental drift
• Formation of mountains
• Oceanic plates usually slide below terrestrial
  plates

13
Continental drift

• Alters habitats
• Reroutes ocean currents
• Changes weather patterns
• Promotes allopatric speciation
• Helps explain why fossils in two different
  regions can be the same

14
Mass Extinctions
Permian extinction
Cretaceous extinction
15
Cretaceous extinction
16
Consequences of mass extinctions

• Evolutionary lineages disappear
• Reduction in the diversity of an ecosystems
• Increase in predators
• Arising of adaptive radiations

17
Mass extinction and predators
18
Adaptive radiation

• An organisms movement into a variety of
  different environments or exploitation of a
  variety of different food sources leads to
  adaptive radiation.
• The mass extinction of dinosaurs gave way to
  adaptive radiation of mammals 65 million years
  ago.

19
Mammalian adaptive radiation
20
The Silversword Alliance
N
Dubautia laxa
1.3 million years
KAUAI 5.1 million years
MOLOKAI
MAUI
OAHU 3.7 million years
Argyroxiphium sandwicense
LANAI
HAWAII 0.4 million years
Dubautia waialealae
Dubautia scabra
Dubautia linearis
21
Exaption

• Using a trait that evolved for one purpose for
  another purpose.
• The lightweight honeycombed bones of early
  non-flying birds were taken advantage of by birds
  that fly.
• Feathers were initially developed for camouflage,
  courtship, or thermoregulation. Later they
  developed for flight.
• Karel Liem, Evolution is like modifying a
  machine while it is running.

22
Evo-devo

• Genes that control development have had a
  profound effect on evolution
• Effect growth rates of particular body parts
• Controls timing of the emergence of particular
  structures
• Controls spatial pattern of particular structures

23
Evolution and development

• Genes control the rate, timing, and spatial
  pattern of development.

24
Evolution and development

• Varying the rate of growth of different body
  regions leads to morphological changes.

25
Heterochrony and salamanders

• Foot growth gets turned off later in ground
  dwelling salamanders.
• Paedomorphosis

26
Changes in spatial pattern

• Homeotic genes, such as Hox genes control spatial
  organization of body features.

27
(No Transcript)
28
New developmental genes
29
Gene regulation
30
Mollusc eye evolution
Evolved complexity
Pigmented cells (photoreceptors)
Pigmented cells
Epithelium
Nerve fibers
Nerve fibers
Eyecup
Patch of pigmented cells
Slit shell Pleurotomania
Limpet Patella
Cornea
Fluid-filled cavity
Cellular fluid (lens)
Epithelium
Optic nerve
Pigmented layer (retina)
Optic nerve
Pinhole camera-type eye
Eye with primitive lens
Marine snail Murex
Nautilus
Cornea
Lens
Retina
Squid Loligo
Optic nerve
Complex camera-type eye
31
Recent
Equus
Hippidion and other genera
Pleistocene
Nannippus
Pliohippus
Neohipparion
Hipparion
Pliocene
Sinohippus
Megahippus
Callippus
Archaeohippus
Merychippus
Miocene
Anchitherium
Hypohippus
Parahippus
Miohippus
Oligocene
Mesohippus
Paleotherium
Epihippus
Propalaeotherium
Pachynolophus
Orohippus
Eocene
Key
Grazers
Hyracotherium
Browsers