Ch. 15 Notes

What evidence did Charles Darwin gather that led to his theory?

What is artificial selection What is artificial selection? How did this concept contribute to Darwin’s ideas on natural selection?

Four Principles of Natural Selection 1) Variation - 2) Heritability - 3) Overproduction - 4) Reproductive Advantage -

Compare and contrast evolution and natural selection What is similar? What is different? -Evolution -Natural Selection

Evolution Evidence The theory of evolution states that all organisms on Earth have descended from a common ancestor

The Fossil Record (Fig. 15.4 p. 423) Support for Evolution The Fossil Record (Fig. 15.4 p. 423) Fossils show that ancient species share similarities with species that live on Earth today

Glyptodont Armadillo

2. Comparative Anatomy (Fig. 15.6 p. 425) a) Homologous structures develop from similar tissues in early developmental stages of the organism, but meet different needs in the adult.

Homologous Structures

Fig. 15.6 on p. 425 Q: What is similar about each of these? Similar bone structure, from same tissue  Q: What is different about each of these? Perform different functions – grab, walk, fly

b) Vestigial structures are features of ancestors that no longer have a function for that species and will become smaller over time until they are lost Ex: Humans → appendix, tailbone (Table 15.2 p. 425) Snakes →tiny bones where legs used to be

Vestigial Structures

Other Vestigial Structures Vestigial Pelvis bone and femur in whales

Other Vestigial Structures

Ex: eagle wing vs. beetle wing bird wing vs. bat wing c) Analogous structures look similar in appearance and function, but are developed from anatomically different parts They are used for the same purpose and similar in construction, but not inherited from a common ancestor. Ex: eagle wing vs. beetle wing (Fig. 15.7) bird wing vs. bat wing

Analogous Structures

3. Comparative Embryology (Fig. 15.8 p. 426) Embryology is the study of embryos Embryo = early, pre-birth stage of an organism’s development Vertebrate embryos have similar structures during certain stages of development, but become totally different structures in the adult form.

Comparative Embryology

Comparative Embryology Human embryo Chick embryo (LM) Pharyngeal pouches Post-anal tail

Q: What do similarities in early development indicate? The organisms have similar genes controlling early development. Q: What do these similar genes indicate? These organisms have a common ancestor. Q: Why do the embryos become different as they develop? Different genes start to contribute or become “expressed” in the organism.

4. Comparative Biochemistry (Fig. 15.9 p. 427) Evolutionary theory predicts molecules in species with a recent common ancestor should share certain amino acid sequences. The more closely related the species are, the more amino acid sequences they have in common.

5. Geographic distribution (Fig. 15.10 p. 427) Evolution is linked to climate and plate tectonics which explains many ancestral relationships and geographic distributions seen in fossils and living organisms. For example: South American animals are more similar to other South American animals than to animals in Europe.

Mara – South America Rabbit – Europe

Adaptation An adaptation is a trait influenced by natural selection that increases an organism’s reproductive success.

Fitness: The ability of an organisms to survive and reproduce how much a certain trait appears in the next generation; measured by the amount of offspring

Camouflage: adaptation that allows a species to blend in with their environment. Why? Hide from predators/prey, more survive to reproduce Ex: Arctic fox (Fig. 15.11 p. 428)

Leafy sea dragon

Mimicry: one species changes to look like another species Ex: Harmless snake “mimics” a poisonous snake so predators leave it alone (Fig. 15.12 p. 429)

California Kingsnake Western Coral Snake (poisonous)

Antibiotic resistance: Some species of bacteria that originally were killed by antibiotics (like penicillin) have evolved to be drug resistant For nearly every antibiotic, there is at least one species of resistant bacteria

Example: Tuberculosis (TB)

Section 15.3

Mechanisms of Evolution 1. Genetic Drift A random change in the frequency of an allele in a population NOT due to natural selection. More likely to occur in small populations.

a. Why does genetic drift have its greatest effects in small, isolated populations?

Mechanisms of Evolution Genetic Drift 2. Founder effect: a small group separates from the population and lives somewhere else they carry a subset of the population’s gene Ex: Amish community

Mechanisms of Evolution Genetic Drift 3. Bottleneck: population declines to a very low number and then rebounds the gene pool of the rebound population is similar to the original population

Northern Elephant Seals

Ex: Northern Elephant Seals 3. Bottleneck Effect Ex: Northern Elephant Seals Large population  overhunting  20 Total Population eventually recovered in size Loss of genetic variation Could hurt long-term survival of species

3. Bottleneck Effect - Cheetahs

Mechanisms of Evolution 4. Remember mutations? A random change in a sequence of DNA. A small population with a lot of mutations has the greatest potential for evolution

Mechanisms of Evolution Natural Selection How does it alter phenotypes?

Mechanisms of Evolution 1. Stabilizing selection: selection against extreme expressions of a trait, selection for the average Ex: birth weight in human babies

Mechanisms of Evolution 2. Directional selection: selection toward one extreme of a trait Ex: Galapagos finches - large beaks during drought Peppered moths - color

Mechanisms of Evolution 3. Disruptive selection: selection against the average, selection for both extremes Ex: Cichlid fish size - males

Mechanisms of Evolution 4. Sexual selection: selection of a trait in males to attract a mate and intimidate other males Ex: peacocks

Isolation 1. Reproductive Isolation Some members of a population change so much that they can no longer produce offspring with members of the original population.

Different mating patterns Eastern meadowlark and Western meadowlark Different mating patterns Liger Sterile

2. Speciation For speciation to happen, a population has to move away and then be reproductively isolated.

2. Speciation Ex: Allopatric Speciation   A physical barrier divides one population into 2 or more populations Abert squirrel South Rim Kaibab Squirrel North Rim

Patterns of Evolution 1. Adaptive Radiation = Divergent Evolution The evolution of a new species in a relatively short period of time one species evolves into several different forms that live in different habitats homologous structures

Adaptive Radiation

Patterns of Evolution 2. Coevolution A close relationship between 2 species The evolution of one species influences the evolution of the other

Coevolution Datura Plant & Hawk Moth

Patterns of Evolution 3. Convergent Evolution Unrelated species evolve similar traits even though they live in environments that are really far apart similar ecology and climate analogous structures

3. Convergent Evolution Unrelated species evolve similar adaptations, due to environmental pressures (natural selection) These adaptations may look similar from the outside, but actually evolve independently from each other Ex: sharks, dolphins, seals, penguins

Remember Analogous Structures? Similar in appearance and function, but are developed from anatomically different parts Evidence for convergent evolution Ex: octopus eye versus vertebrate eye (both complex eyes

How fast does speciation happen? 1. Gradualism: Evolutionary change occurs gradually, over long periods of time

How fast does speciation happen? 2. Punctuated Equilibrium Patterns of long periods of stability (no change) interrupted by episodes of rapid change

How fast does speciation happen?

Evolution can follow both patterns, depending on the situation and the time in evolutionary history