1. Daily Science
Give one piece of evidence for evolution we’ve been discussing, besides fossils!
Answer: embryology, geographic distribution, vestigial organs, DNA/molecular evidence, homologous structures
What does descent with modification mean?
Answer: it means all things have a common ancestor and have descended and modified (adapted through natural selection) and changed over time

2. Today’s Learning Target
Explain the differences between natural and artificial selection and connect to Darwin’s ideas of genetic inheritance.

3. Barreleye Fish
Have a transparent forehead and green orbitals for eyes to spot prey from above. The 2 spots near the mouth are for filtering chemicals in the water.

4. Artificial Selection, Natural Selection, and Adaptation
Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection
Darwin then described four observations of nature and from these drew two inferences
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5. Terminal bud Lateral buds Cabbage Brussels sprouts Flower clusters
Fig. 22-9
Terminal
bud
Lateral
buds
Cabbage
Brussels sprouts
Flower
clusters
Leaves
Kale
Cauliflower
Figure 22.9 Artificial selection
Stem
Wild mustard
Flowers
and stems
Broccoli
Kohlrabi

6. Artificial Selection

7. Observation #1: Members of a population often vary greatly in their traits
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8. Observation #2: Traits are inherited from parents to offspring
Observation #3: All species are capable of producing more offspring than the environment can support
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9. Observation #4: Owing to lack of food or other resources, many of these offspring do not survive
Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals
Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations
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10. Darwin was influenced by Thomas Malthus who noted the potential for human population to increase faster than food supplies and other resources
If some heritable traits are advantageous, these will accumulate in the population, and this will increase the frequency of individuals with adaptations
This process explains the match between organisms and their environment
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11. Natural Selection: A Summary
Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals
Natural selection increases the adaptation of organisms to their environment over time
If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species
Video: Seahorse Camouflage
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12. Both are mantids but have evolved in different environments.
Fig
(a) A flower mantid
in Malaysia
Both are mantids but have evolved in different environments.
(b) A stick mantid
in Africa
Figure Camouflage as an example of evolutionary adaptation

13. Note that individuals do not evolve; populations evolve over time
Natural selection can only increase or decrease heritable traits in a population
Adaptations vary with different environments, may be beneficial in one but detrimental in another
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14. Direct Observations of Evolutionary Change
Concept 22.3: Evolution is supported by an overwhelming amount of scientific evidence
New discoveries continue to fill the gaps identified by Darwin in The Origin of Species
Direct Observations of Evolutionary Change
Two examples provide evidence for natural selection: the effect of differential predation on guppy populations and the evolution of drug-resistant HIV
See pages
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15. Natural selection does not create new traits, but edits or selects for traits already present in the population
The local environment determines which traits will be selected for or selected against in any specific population
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16. The Fossil Record
The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time
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17. Fig
See changes in the location and angles of the spines of the head shield 2 4 4 6 4
Bristolia insolens 8 3
Bristolia bristolensis 10 12 3
Depth (meters) 2
Bristolia harringtoni 14 16 18 1
Bristolia mohavensis 3
Figure Fossil evidence of evolution in a group of trilobites 2 1
Latham Shale dig site, San
Bernardino County, California

18. The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record
Paleontologists have discovered fossils of many such transitional forms
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19. See the loss of hind limbs over time from land mammals to aquatic

20. Bird Evolution- Transition Fossils

21. Whale Evolution- Transition Fossils

22. Horse Evolution- Transition Fossils

23. Homology is similarity resulting from common ancestry
Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor
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24. Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat
Fig
Humerus
Radius
Ulna
Carpals
Metacarpals
Figure Mammalian forelimbs: homologous structures
Phalanges
Human
Cat
Whale
Bat

25. Fig
Comparative embryology reveals anatomical homologies not visible in adult organisms
Pharyngeal
pouches
Post-anal
tail
Figure Anatomical similarities in vertebrate embryos
Chick embryo (LM)
Human embryo

26. Guess The Embryo

27. Vestigial structures are remnants of features that served important functions in the organism’s ancestors
Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor
Like the forelimbs of humans and whales, these genes have very different functions
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