Chapter 22 Part 2: Evidence for Darwinian Evolution

Info from Class Video

Concept 22.3

Evolution is supported by an overwhelming amount of scientific evidence

4 types of data document pattern of evolution

direct observations, homology, fossil record, biogeography

1 example direct observation evidence for natural selection

natural selection in response to introduced plant species

2 example direct observation evidence for natural selection

evolution of drug-resistant bacteria

soapberry bugs how feed on seeds in fruits

“beaks”

feeding for soapberry bugs most effective when

beak length is closely matched to seed depth within fruit

southern Florida soapberry bugs fruit they eat and beak length

native balloon vine w larger fruit → longer beaks

central Florida soapberry bugs fruit they eat and beak length

introduced goldenrain tree w smaller fruit → shorter beaks

correlation between fruit size and beak size also observed in

Louisiana, Oklahoma, Australia

in all cases, beak size has evolved in populations that feed on

introduced plants w fruits that are smaller/larger than native fruits

Staphylococcus aureus

bacteria common on people

MRSA

methicillin resistant S. aureus - dangerous pathogen

S. aureus resistance to penicillin

1945 - 2 yrs after it was widely used

S. aureus resistance to methicillin

1961 - 2 yrs after it was widely used

how does methicillin work

inhibits protein used by bacteria to produce cell walls

how MRSA bacteria combat methicillin

use different protein in cell wall production

MRSA strains are now resistant to many

antibiotics

Natural selection does not

create new traits

Natural selection does

edit or select for traits already present in population

what determines which traits will be selected for/against in any specific population

current, local environment

Homology

similarity resulting from common ancestry

Homologous structures

anatomical resemblances represent variations on structural theme present in common ancestor

what does comparative embryology reveal

anatomical homologies not seen in adult organisms

example comparative embryology vertebrates

all have post-anal tail and pharyngeal arches

vestigial structures

remnants of features that served important functions in organism’s ancestors

examples of homologies at molecular level

genes shared among organisms inherited from a common ancestor

evolutionary trees

hypotheses about relationships among different groups

homologies form nested patterns in

evolutionary trees

what can evolutionary trees be made using

diff types data ex: anatomical and DNA sequence data

branch points on evolutionary tree

points of divergence based on particular traits

a different cause of resemblance

convergent evolution

convergent evolution

evolution of similar/analogous features in distantly related groups

analogous traits arise when

groups independently adapt to similar environments in similar ways

convergent evolution does not provide info about

ancestry

examples convergent evolution

sugar gliders from australia - marsupial mammal

flying squirrels from north america - placenta mammal

fossil record provides evidence of

extinction of species, origin of new groups, changes within groups over time

fossils document important

transitions

fossils example document transition

from land to sea in ancestors of cetaceans

biogeography

scientific study of geographic distribution of species, provides evidence of evolution

Pangaea

Earth’s continents formerly united in single large continent - since separated by continental drift

understanding continent movement and modern distribution of species allows us to predict

when and where different groups evolved

Endemic species

species not found anywhere else in world

islands have many endemic species often

closely related to species on nearest mainland/island

darwin explained species from mainland colonized islands and

gave rise to new species as they adapted to new environments

Mosquitoes resistant to DDT

resistance to insecticides in about 1 year