major patterns of evolution Evolution test 1

2 reasons why phenotypes are similar in different species:

homology and Homoplasy

Homology

phenotypes are similar because they are inherited from a common ancestor

Homoplasy

phenotypes are similar but are independently evolved

vestigial structure

a reduced, non-functional, or significantly less-functional body part or feature of an organism that is a leftover from its ancestors.

what are vestigial structures strong evidence for?

descent from a common ancestor

ex of homology

limb bones in all modern tetrapods

Evolution acts on

available variation

Ancestral traits can be modified…., which makes them ….

different functions

homologous- they are evolved and share genetic and developmental origin

convergence

A type of homoplasy.

Independent evolution of similar traits because of common selection pressure

Bones in mammal legs and mammal flippers

• Shape of mammal limbs and insect limbs

• are homologous (shared with common mammal ancestor)

• convergent (not shared with common ancestor)

parallel evolution

– Homoplasy that results from similar (parallel) origins

– Not the same as convergence, or homology

– The same change happens independently, by the same process, in different organisms

Selection acts on

available variation

Can evolution of totally new features happen? What is more common?

yes, but it is rare

• it is more common that existing features are modified for new purposes

Different characters evolve at same/different rates?

different

when do characters evolve slowly?

Characters with strong functional relationships (many parts that have to be coordinated to function) evolve slowly

mosaic evolution

leads to?

characters often evolve independently of one another.

– This leads to species composed of some fast evolving characters and some slow-evolving characters

conserved evolution

ex?

slow evolution

• frog body form

highly variable evolution

ex.

fast evolution

• reproductive biology

slow, smooth transitions in traits happen when evolution is? Where can it be seen?

gradual

• seen in fossil records

Gradualism

species continuously change (slowly) over their history

Punctuated Equilibrium

hypothesis: species are static for most of their history, then undergo rapid change during speciation

– There is still a debate over which is most important

stratigraphy

tells us the relative order of geological changes

Radiometric

dating tells us the absolute age of igneous rock layers

• Different isotopes cover different time spans

C isotope covers

Rubidium:

• 14.5 life= 5730 yrs

• 87.5 life-48.8 billion

The geological time scale name based on

distinctive fossil taxa

The fossil record is highly incomplete. Why?

– Mostly hard parts fossilize (*Exceptions: amber fossils and imprints)

* – Only some environments will allow fossilization BEFORE decomposition

– Rock needs to persist over time (older fossils harder to find)

– Rock must be accessible for discoveries

• bc of that major discoveries are still common

How can we predict where to find certain fossils?

• its not random

• . Rocks of the right age -Use phylogeny and common ancestry to guess (~375 mya in this case)

• 2. Rocks of the right type

  -Sedimentary rocks preserve well; igneous & metamorphic don’t

  • Needs to be from right ancient environment (stream in this case)

• 3. Rocks exposed on the surface

Tiktaalik fossil?

a transitional fossil with traits from both fish and early land-dwelling tetrapods (four-limbed vertebrates), providing crucial evidence for the evolutionary transition from aquatic to terrestrial life

• key features like a neck, lungs, strong ribs for body support, and fins with bones like wrist and elbow, which foreshadowed the limbs and walking ability of land animals

what did the tikaalik do for paleontology

• Confirmed predictions of paleontology

– Found at the right time (375 Myr)

– Found in the right ancestral environment (stream)

• Showed key transition that only fossils can tell us

• The fact that we can predict where transitional fossils found is strong evidence for evolution

Phenotypic change in the fossil record which shows

Evidence for evolutionary change over time

can we see variation in rates of evolutionary change over time? of so, how

yes,

evolution rates high at short intervals

evolution rates low at long intervals

variation rates in evolutionary can

change over time

• paradox of stasis

evolutionary change doesnt accumulate until

after 1 Myr

is evolution progressive by definition?

Evolution is not by definition progressive

• there is not an innate
  tendency for organisms to
  evolve towards a goal

• This misconception
  persists, usually with the
  idea that humans are the
  goa

contingency vs predictability