Steps of Chemical Evolution
- Gasses of the primitive atmosphere formed small organic molecules
- Small molecules combined to form large macromolecules
- Only RNA might bave been needed to form the first cells
- Protocells made of proteins and lipids could metabolize by using oceanic organic molecules, but could not produce
- True cell can reproduce and has DNA as its genetic material
Miller Experiment
1953
Biological Evolution
A change in population or species overtime, with 2 important points:
- Living things descend from a common ancestor and thus have common chemistry
- Living things adapt to their environment
Adaptation
A characteristic that helps an organism survive and reproduce in its environment
Evidence to support the theory of evolution by common descent
- fossil evidence
- biogeographical evidence
- anatomical evidence
- biochemical evidence
Fossils
Traces of past life
Fossils allow us to trace the descent of a particular group of organisms
Charles Darwin, an English naturalist, relied on fossils to formulate the theory of evolution
What have we learned from fossil records
- life progressed from simple to complex
- prokaryotes are the first life forms seen in the fossil record, followed by unicellular eukaryotes, then multicellular eukaryotes
- fish evolved before terrestrial plants and animals
- non-flowering plants preceded flowering plants
- amphibians preceded reptiles
- dinosaurs are directly linked to birds
Biogeographical Evidence
- the study of distribution of plants and animals throughout the world
- supports the hypothesis that organisms originate in one locale and then may spread out
- different life forms are expected whenever geography separates them
- islands demonstrate this because they have many unique life forms due to geographical isolation
Anatomical Evidence
Common decent hypothesis offers plausible explanation for anatomical similarities among living organisms
Homologous Structures
anatomically similar and inherited from common ancestors, eg. vertebrate forelimbs
Analogous structures
serve the same function but do not share a common ancestry and thus are not anatomically similar, eg wings of a bird and wings of an insect
Vestigial structure
are fully developed in one group but are reduced and may have no function in another group, eg, whales have a vestigial pelvic girdle and legs
Biochemical evidence
- almost all living things use the same biochemicals (DNA, ATP, etc)
- living things use the same triplet genetic code (codon)
- living things use the same 20 amino acids in their proteins
- living things share many of the same genes
Natural Selection
Darwin’s theory that describes a mechanism by which a species becomes adapted to its environment:
- variation: there must be a physical variations in phenotype that can be passed from generation to generation
- competition: there must be competition for limited resources. Those better adapted will survive and reproduce (Survival of the Fittest)
- adaptation: subsequent generations will see an increase in individuals with the same adaptation as long as the environment remains unchanged
Humans on Earth
Genus: General Characteristics: Homo
Species: Specific Characteristics: Sapiens
Primates: Tree Dwellers
Characteristics:
- opposable thumbs
- stereoscopic vision (depth perception)
- well developed brain
- reduced number of offspring (usually single-birth) with an increased period of parental care
- emphasis on learned behavior and social interactions
Primates: 2 Suborders
- prosimians: lemurs, tarsiers, and lorises
2. anthropoids: monkeys, apes and humans
Evolution of hominids - split from apes (we came down from trees)
- bipedal, while apes walked on knuckles
- flatter faces with more pronounced chin than apes
- brain size 3X size of apes
HOMINIDS SPLIT FROM APE LINE OF DESCENT 7MYA - WHILE WE SHARE A COMMON ANCESTOR, WE DID NOT COME FROM APES!
Suggested fossils of the first hominids (6-7 MYA)
Australopithecines
A group of hominids that evolve and diversified in eastern Africa ~ 3 MYA
- some had slight frames and others were robust with massive jaws that fed on plant materials
- walked upright
- limbs proportions are ape-like
- small brain
- famous skeleton “Lucy” is fro this group
AUSTRALOPITHECUS AFRICANUS IS THE MOST LIKELY ANCESTRAL CANDIDATE FOR EARLY HOMO
Characteristics of Homo
- brain size is 600 cm3 or greater
- evidence of tool use
- jaw and teeth resemble humans
Early Homo representatives
- homo habilis
- homo erectus
Later Homo representatives
- neandertals
- cro-magnons
Early Homo: Homo Habilis
- lived 2.0-1.9,MYA
- large brain with enlarged speech area
- omnivorous (hunters and gatherers)
- primitive tools, culture may have existed
Early Homo: Homo Erectus
- lived 1.9 - 0.3 MYA
- larger brain, flat face with nose projected
- tall and stood erect, had striding gait
- may have migrated from Africa to Europe and Asia
- had advanced tools and used fire (systematic hunters)
language may have evolved
Early Homo: Homo Neadertalenis
- liked 200,000 yrs BP
- massive brow ridges, protruding nose, jaw, teeth
- brain slightly larger than humans
- shorter, thicker, more muscular limbs than humans
- culturally advanced, many tools, were hunters
Early Homo: Cro-Magnons
- first and oldest Homo Sapiens - looked human
- liked 100,000 yrs BP
- compound tools (stone fitted to wood, spears)
- may have caused extinction of large mammals
- hunted cooperatively, may have had language
- were artistic
