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

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

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.

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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

Artificial Selection

Observation #1: Members of a population often vary greatly in their traits Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Observation #2: Traits are inherited from parents to offspring Observation #3: All species are capable of producing more offspring than the environment can support Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Both are mantids but have evolved in different environments. Fig. 22-12 (a) A flower mantid in Malaysia Both are mantids but have evolved in different environments. (b) A stick mantid in Africa Figure 22.12 Camouflage as an example of evolutionary adaptation

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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 460-461 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Fossil Record The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 22-15 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 22.15 Fossil evidence of evolution in a group of trilobites 2 1 Latham Shale dig site, San Bernardino County, California

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

See the loss of hind limbs over time from land mammals to aquatic

Bird Evolution- Transition Fossils

Whale Evolution- Transition Fossils

Horse Evolution- Transition Fossils

Homology is similarity resulting from common ancestry Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat Fig. 22-17 Humerus Radius Ulna Carpals Metacarpals Figure 22.17 Mammalian forelimbs: homologous structures Phalanges Human Cat Whale Bat

Fig. 22-18 Comparative embryology reveals anatomical homologies not visible in adult organisms Pharyngeal pouches Post-anal tail Figure 22.18 Anatomical similarities in vertebrate embryos Chick embryo (LM) Human embryo

Guess The Embryo http://www.pbs.org/wgbh/nova/evolution/guess-embryo.html

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings