Exam quiz 1: Evidence for evolution and Phylogenetic trees (Lecture 1-6)

Darwin & Wallace’s Theories

1. Evolution (species change)

2. Common Descent: common ancestors, diversifies over time

3. Multiplication of Species

4. Gradualism

5. Natural Selection (incl. sexual selection: choosing best mate)

Common Beliefs in Darwin & Wallace’s Time

1. Earth was Young (created in 4004 BC)

2. Species created by God

3. Species were perfect

4. Species were fixed/didn’t vary (essentialism)

5. Species didn’t change

Summaries Darwin & Wallace’s Theories

The gradual diversifying evolution of new species from common ancestors through a process of natural selection.

i.e. Descent with modification

Darwin & Wallace’s vs [Plato, Aristotle, & Lamarck’s] Theories

Plato: Typological Thinking - species are fixed/don’t change. [AKA special creation/intelligent design]

Lamarck: organisms originate through spontaneous generations; evolve into higher organisms over time

Aristotle: Typological Thinking + scale of nature [there are lower & higher life forms]

Darwin/Wallace: organisms have common ancestors & diversify overtime

-> [doesn’t believe in lower/higher life forms because every organism today has evolved for the same amount of time

Evidence of Evolution (5): Transitional Fossils

Intermediate forms in fossil records

E.g. Archaeopteryx: displays ancestral & descendant groups

Transitional fossils in whale evolution: land mammals → contemporary whales have vestigial femurs (proves contemporary whales evolved from land mammals)

Evidence of Evolution (6): Hierarchical Organisation of Life

Life is organized in nested groups of organisms.

E.g. Insects - Beetles & Butterflies | Birds: Falcons & Ducks

Carlos Linnaeus (1707-1778): 1st to classify life → his classification system is used today → consists of (taxonomic - classifying and naming living things) levels nested inside each other.

→ Species (Home Sapiens), genus (Homo), family (Hominidae), order (primates), class (Mammalia), phyllum (chordata), kingdom (Animalia)

Implies: The theory of descent w/ modification predicts the observed hierarchical organisation of life. i.e. common ancestor of birds=com am of falcons/ducks. Common ancestor of Animals=common ancestor of insects/beetles/butterflies

Evidence for Evolution (7): Homology [characteristics in diff organisms w/ similar underlying molecular/anatomical structures or similar developmental processes. Based on shared ancestry.

Anatomical Homology: a manatee’s limbs has finger nails (vestigial trait) like humans. Manatee=ancestor who had nails.

Developmental Homology: Human embryos early development have pharyngeal pouches/tail/gills=we have an ancestor w/ these structures. (Features go away as embryo develops)

Genetic Homology: all organisms use DNA or RNA as genetic material. →common ancestor had DNA or RNA & passed it to all descendants.

Evidence for Evolution (8): Vestigial Traits [useless/rudimentary version of structure that’s important trait to other organisms, sometimes used for a new function].

E.g. some whales today have vestigial femurs/pelvis’=whales evolved from land mammals that have functional limbs.

Vestigial Traits in Embryos: dolphin embryos 24 & 48 days - have hindlimb buds that develop into hindlegs others then go away as dolphin embryo develops. = dolphin’s ancestor has hindlimbs.

Vestigial Traits in Animals:

Vestigial Traits in Humans: