Download Biol 112 LAB REMINDERS Variation in populations Heritability of

9/8/2011
LAB REMINDERS
Biol 112
Lecture 2: Evolution and Natural Selection Natural Selection‐ Darwin’s observations
• PICK UP YOUR TICKET FOR THE HMNH.
• NEXT WEEK GO to the museum
• YOU CAN GO ANYTIME BUT YOUR TA’s will be there during your scheduled lab time (except WED‐ will be there Sunday instead)
• If you want help from a TA it doesn’t have to be yours
• TURN IN YOUR PIN FROM THE MUSEUM
Variation in populations
• Variation exists in populations
• Most organisms have a higher reproductive potential than observed number of offspring
QuickTime™ and a
decompressor
are needed to see this picture.
Pinguicula.org
Heritability of traits
e.g. of non heritable variation
• Hydrangeas grow different colors depending on soil acidity and availability of Aluminum ions.
• Natural selection affects individuals with traits that are inherited (passed on from parents through genes)
• Some traits vary due to environmental factors. These traits would not be subjected to selection because the variation can’t be passed on to offspring
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
Pink or Blue flowers
not a trait that is
inherited through
genes.
Edenscontainer.co
m
Low pH-acidic
High pH-basic
1
9/8/2011
Figure 1.20
Overproduction of offspring
Fungus
Coral Spawning
1 Population with
varied inherited
traits
2 Elimination of
individuals with
certain traits
3 Reproduction of
survivors
QuickTime™ and a
decompressor
are needed to see this picture.
4 Increasing
frequency of
traits that
enhance
survival and
reproductive
success
Noaa.gov
Evolution by Natural Selection
• Inference #1‐ Individuals whose inherited traits give them a higher probability of surviving and reproducing in a particular habitat leave more offspring than others
• Inference #2 This unequal ability of individuals to survive and reproduce leads to an accumulation of these traits in a population over generations
Summary of Natural Selection
• 1. There is variation of traits (morphological, proteins, transcription factors‐ turn genes on/off) in populations
• 2. Differential reproduction‐ A trait allows an individual to survive better and/or reproduce more will produce more offspring
• 3. If that trait is heritable (is based on genetics) more individuals in the population will have that trait in the next generation.
• 4. Natural selection increases adaptations to an environment over time.
Green warbler finch
Certhidea olivacea
Gray warbler finch
Certhidea fusca
Bud-eater
Seed-eater
COMMON
ANCESTOR
Insect-eaters
More points to remember about natural selection
Warbler finches
Figure 1.22
Sharp-beaked
ground finch
Geospiza difficilis
Vegetarian finch
Platyspiza crassirostris
Mangrove finch
Cactospiza heliobates
Tree finches
Insect-eaters
-Evolution occurs at the level of population :
INDIVIDUALS DON’T EVOLVE
-Environments are variable between regions different
adaptations may be more or less advantageous in
different areas
Large tree finch
Camarhynchus psittacula
Small tree finch
Camarhynchus parvulus
Cactus-flowereaters
Seed-eaters
Ground finches
-Environments also change over time resulting in
populations of species adapting to these new conditions.
This may give rise to new species
Woodpecker finch
Cactospiza pallida
Medium tree finch
Camarhynchus pauper
Large cactus
ground finch
Geospiza conirostris
Cactus ground finch
Geospiza scandens
Small ground finch
Geospiza fuliginosa
Medium ground finch
Geospiza fortis
Large ground finch
Geospiza
magnirostris
2
9/8/2011
Figure 22.13a
Direct Observations of Evolutionary Change
FIELD STUDY
Soapberry bugs
MRSA
Pesticide resistance in insects
Soapberry bug with beak
inserted in balloon vine fruit
Figure 22.13b
RESULTS
MRSA‐Methicillin‐resistant Staphylococcus aureus
Beak
10
On native species,
southern Florida
8
Number of individuals
6
4
2
0
Museum-specimen average
10
QuickTime™ and a
decompressor
are needed to see this picture.
On introduced species,
central Florida
8
6
4
2
0
6
7
8
9
Beak length (mm)
Figure 22.14
2,750,000
10
11
• S. aureus is a common bacteria found on skin
• Antibiotics (Methicillin) use to kill off most S. aureus by inhibiting a protein used in the cell wall.
• Those that survived had a variation in the protein used to make the cell wall that allowed them to survive and reproduce in the presence of methicillin
• MRSA strains are now resistant to many antibiotics
1
250,000 base pairs
Pesticide resistance in insects
2,500,000
Chromosome map
of S. aureus clone USA300
500,000
Major pest on potato crops
Key to adaptations
2,250,000
Methicillin resistance
Ability to colonize hosts
750,000
Why? Live on plants with high toxicity thus have existing variation in toxic tolerance
Increased disease severity
2,000,000
Increased gene exchange
(within species) and
toxin production
1,750,000
1,500,000
QuickTime™ and a
decompressor
are needed to see this picture.
Populations have become resistant to 52 different pesticide compounds
1,000,000
High fecundity
Colorado potato beetle Complicated life cycle
1,250,000
3
9/8/2011
Evidence for evolution
•
•
•
•
•
•
•
1. Homology 2.Hierarchial organization of life 3. Embryological similarities
4. Vestigal characters
5.Convergence
6. Fossils and intermediate forms
7. Geographic distributions
Homology is similarity resulting from common ancestry
Figure 22.15
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
© 2011 Pearson Education, Inc.
• Comparative embryology reveals anatomical homologies not visible in adult organisms
• Evolutionary trees are hypotheses about the relationships among different groups
• Homologous traits are used to infer relationships in a tree
• Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data
Pharyngeal
pouches
Post-anal
tail
Chick embryo (LM)
Homologies and “Tree Thinking”
Human embryo
Figure 22.16
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Convergent Evolution
QuickTime™ and a
decompressor
are needed to see this picture.
• Convergent evolution is the evolution of similar, or analogous, features in distantly related groups
• These traits often evolve under similar selective pressure or in similar habitats.
© 2011 Pearson Education, Inc.
4
9/8/2011
Figure 22.18
Eyes in cephalopods and vertebrates‐ they function similarly (form images) but differ in structure.
Marsupial
NORTH
AMERICA
Sugar
glider
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
AUSTRALIA
Flying
squirrel
Placental
Figure 1 Eye development and degeneration.
Vestigial organs
• Organs derived from an ancestor that no longer have a function (or a much reduced function).
– Some cave dwelling species still have eyes even though they aren’t functional
Y Yamamoto, W R Jeffery Science 2000;289:631-633
Published by AAAS
• The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time
• Fossils can document important transitions. For example, the transition from land to sea in the ancestors of cetaceans
Other
even-toed
ungulates
Hippopotamuses
†Pakicetus
†Rodhocetus
QuickTime™ and a
decompressor
are needed to see this picture.
Common
ancestor
of cetaceans
†Dorudon
Living
cetaceans
70
© 2011 Pearson Education, Inc.
60
50
© 2011 Pearson Education, Inc.
40
30
20
10
Millions of years ago
0
Key
Pelvis
Femur
Tibia
Foot
5
9/8/2011
Fig. 3. Biogeographic reconstructions.
Biogeography
• Biogeography, the geographic distribution of species, provides evidence of evolution
• Earth’s continents were formerly united in a single large continent called Pangaea, but have since separated by continental drift
• An understanding of continent movement and modern distribution of species allows us to predict when and where different groups evolved
E C Teeling et al. Science 2005;307:580-584
Published by AAAS
© 2011 Pearson Education, Inc.
QuickTime™ and a
decompressor
are needed to see this picture.
6