Comprehensive and well-organized notes on the BIO1004S theory, with information consolidated from 3 different textbooks, lectures, and extra reading material. Written by a student who achieved an upper first for the course.
Samenvatting Hoofdstuk 12 van Biology a Global Approach 11th edition
Samenvatting Hoofdstuk 8 van Biology a Global Approach 11th edition
Samenvatting Hoofdstuk 7 van Biology a Global Apprach 11th edition
All for this textbook (58)
Written for
University of Cape Town (UCT)
BIO1004S (BIO1004S)
All documents for this subject (8)
Seller
Follow
Ednabutler
Reviews received
Content preview
0
Evolution → "descent with modification"
1. Historical Background
• Existence of life originally explained by creationism/religion/supernatural intervention
• Naturalistic models (based on logic, philosophy): new species are a result of natural causes only
◦ Plato (428BC): species are unchanging, fixed.
◦ Aristotle (384BC): developed "scale of nature" → natural world arranged on ladder, showing progression
from imperfect to most perfect (increasing complexity: inanimate matter to humans).
• Evolutionary ideas made comeback in 18th century.
• 1831 HMS Beagle: Charles Darwin travels to SA, Aus, South America.
◦ Studied, logged local plants/animals and geological formations
◦ Galapagos Islands, 950km from S. America:
‣ Mainland had 1 species, while islands had 14.
‣ Species were similar but nonidentical finches, each well-suited for its environment/role
• Ate large seeds = large, tough beaks. Ate insects = thin, sharp beaks, etc.
‣ Observed similar patterns with tortoises (differing in shell shape) and many plants
‣ "What is the mechanism by which each population acquired adaptations?"
◦ Argentina, S. America:
‣ Found fossils similar to modern forms
• e.g Glyptodonts → extant Armadillos
‣ "Why have species gone extinct only to be replaced by more successful ones?"
• Key influencers
◦ Carl Linnaeus: the founder of taxonomy, the nested system of classifications
◦ George Cuvier: recognised fossils as evidence of earlier life, established extinctions as fact
◦ Charles Lyell: friend of Darwin, influenced his thinking about gradual bio evolution
‣ promoted uniformitarianism: geological features caused by gradual change, not catastrophic events
◦ Jean Baptiste de Lamarck: the main evolutionary theorist before Darwin
‣ Stated evolution takes place, suggested an gradualism mechanism
• 'Species are plastic, can be modified'
• 'The disuse/use of a structure can be passed on', e.g giraffes have long necks due to ancestors
stretching them a lot
‣ Incorrect mechanism: acquired characteristics not inherited
◦ Thomas Malthus: interested in growth of human populations
‣ Stated factors that limit exponential population growth (disease - MALaria! - and food).
‣ Made Darwin realise that far more offspring are produced than can survive; competition for resources
• Influences (DADFGG)
◦ Diversity of life
◦ Adaptations
◦ Distributed species differ in different regions
◦ Fossil and extant forms
◦ Geology
◦ Galapogos Islands research
• Took a scientific approach: induction (form hypothesis, facts), deduction (if true, certain things should follow),
and testing
Notes: Don't need to know Charles Darwin biography.
Alfred Wallace independently reached similar conclusions to Darwin at roughly the same time.
, 2. Evidence for Evolution
Deduction phase of testing: certain things should be true, if evolutionary hypothesis is correct.
A) The Earth should be old
• Earth was created about 4.5 bn years ago. Dated via:
◦ Zircon rock in Australia (4.1 bn years old), moon rocks, meteorites, fossils
‣ Using radiometric dating: relies on half-life decay of radioactive elements to date rocks and materials
‣ Using stratigraphy: the study of rock layers from which relative dates can be extrapolated
• Life began nearly 4 bn years ago
◦ While the oldest known rocks/fossils are approximately 3.5 bn years old...
‣ 3.5byo Stromatolite (SA): layers of cyanobacteria that trap/precipitate sediments
‣ 2.1 byo Francevillian biota (Gabon): first multicellular life
◦ Miller & Urey generated amino acids, biomolecules under early-Earth conditions (suggesting it began earlier!)
‣ Organic molecules could have been introduced via primordial soup, meteorites (found with organic
traces), or hydrothermal events
‣ Panspermia: life exists universally, is distributed via space dust, meteoroids, comets
B) Fossil evidence should reflect evolution
• Fossil: preserved remains of ancient organisms
◦ Calcium/bone minerals replaced with rock via diagenesis (∴ only hard parts preserved)
◦ Gives info on patterns, successive evolutionary change, origin, diversity, extinction
‣ BUT very incomplete - most organisms never fossilize
• Records help document extinct species & histories of extant species, e.g Horse fossil records indicate changes in
lineage: reduction of toed feet to hooves
• Shows how new groups arise via gradual modification of existing
◦ Reflect change in composition
◦ Reflect change in complexity
◦ Reflect increasing diversity
C) Characteristics should reflect evolutionary tree
• 'Descent with modification" → history of life forms a branching tree, where all 3 domains of life are united by
LUCA.
◦ This evolutionary theory predicts more related groups have more recent common ancestors
‣ ∴ morphological, physiological, biochemical, and genetic similarities may reflect shared evolutionary
ancestry. Similar characteristics due to relatedness are homologies.
‣ Can work backwards to find relation based on shared features
• Morphological/anatomical
◦ Homologous characteristics: derived from the same structure or shared due to evolutionary history/
shared ancestor.
‣ Don't necessarily have same function, but same structure, relationship to other features, and
development
‣ E.g While forelimbs of whales, humans, birds, and dogs look different ( adapted to function in different
environments), the bone structure is very similar ∴ likely all share a common ancestor
‣ E.g the forelimb of tetrapods all share the same set of bones.
‣ Vestigial structures: reduced/non-functional structures that are homologous to useful structures in
other organisms. Evolutionary 'leftovers'.
• E.g human tailbone (vestigial tail), whale hind limbs, python limb bones
◦ Analagous characteristics: superficially similar but have independent evolutionary origins
‣ A result of convergent evolution: organisms not closely related evolving similar traits as a result of
having to adapt to similar environments/ecological niches.
• E.g Shark (evolved from fish), Ichthyosaur (from reptile), and Porpoise (from mammal) have very
similar body shape that helps rapid swimming; bat and bird wings; marsupial and placental mole
body structure
‣ Homoplasy: character thats shared by a set of species, but not present in their common ancestor
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Ednabutler. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.97. You're not tied to anything after your purchase.
