nature of science. theory: an explanation for many related observations based on extensive...

Nature of Science

Theory:

• An explanation for many related observations based on extensive scientific and experimental evidence in many conditions.

Science Religion

Microevolution vs. Macroevolution

Objective 1: Distinguish between the process of evolution (microevolution) and

theory of evolution (macroevolution).

Evolution: (Microevolution)• Definition: the change in gene frequency

of a population over time.

Evolutionary Theory: (Macroevolution)• The theory that life originated from one

common unicellular ancestor and became diverse through natural selection and speciation.

Necessary VocabularyVariation: differences between individual members of a

population. (Physical, behavioral, biochemical,etc)

Remember: Variation occurs from...• Genetic Mutations• Crossing Over• Independent Assortment• Fertilization

Necessary Vocabulary

Adaptation: inherited trait that increases an

organism's chances of survival and reproduction in a particular environment.

Necessary Vocabulary

Species:• An interbreeding, or

potentially interbreeding, population that produces healthy, fertile offspring.

Necessary Vocabulary

Population: A group of organisms of the same

species living in a specific area.

Story TimeThe ancestors of giraffes had short necks. In order to eat leaves high up in the trees, individuals had to stretch their necks. As a direct result of this activity, the offspring of these individuals had longer necks. They, too, stretched their necks to reach even higher leaves, and transmitted their even longer necks to their offspring. Over time, as a result of the striving of individual giraffes, modern-day giraffes have very long necks.

Story TimeThe ancestor of modern giraffes would have been a mammal with a short neck. In the ancestral population, a mutation arose that lengthened the neck of any animal that happened to harbor the mutation. These individuals were able to reach leaves higher in the trees than were other individuals. As a result, they were able to eat more and produced more offspring. Gradually, the long-neck mutation spread through the population. Sometime later, another mutation arose, which lengthened necks even more, and it spread through the population in a similar manner. Eventually, a number of mutations, each of which helped lengthen necks, spread throughout the population, resulting in the long necks we see today.

Objective 2: Describe and Identify the conditions necessary for natural selection to occur.

***Natural Selection***

• In 1859, after 15 years of observations and research, Charles Robert Darwin published On the Origin of Species. In this book, he introduced his "Theory of Evolution" based on Natural Selection.

***Natural Selection***

This theory states that the following conditions must exist for evolution to occur...

1. There must be VARIATION in a population.2. There is a change in the environment. (The video

calls this… Struggle for existence)3. Those organisms with favorable variation survive.4. Individuals who survive, reproduce, and pass on the

favorable variation to their offspring.

***Adaptations occur because of Natural Selection***

Natural Selection vs. Artificial Selection

Obj. 4: Compare & contrast natural and artificial selection.

Natural Selection vs. Artificial Selection

• Natural Selection: conditions in nature determine what survives and reproduces.

• Resulting adaptations allow better survival in the organisms' natural environment.

• Example: – Peppered Moth– Darwin’s Finches– White Lizards of New Mexico

Natural Selection vs. Artificial Selection

• Artificial Selection: humans decide what survives and reproduces.

• Resulting adaptations serve the needs of humans.

• Examples:– Farmers breed cows to produce more milk.– Humans breed horses for quickness and strength. – Genetically Modified Foods

SpeciationObj. 6: Describe a scenario where natural selection leads to speciation.

Speciation

What is speciation? • The evolution of one or

more species from an original ancestor species.

SpeciationWhat are the three-steps in order for speciation

to occur?

Step 1: Isolation of population

Step 2: Adaptation/Evolution

Step 3:. Reproductive Isolation

Evidence for EvolutionObj. 7: Identify & explain evidence of evolution

including trends in history of life on earth.

Evidence for Evolution

• Degree of relatedness between two species depends on how long ago they shared common ancestors. To determine relatedness, scientists can use: – Comparative Anatomy– Comparative Embryology– Comparative DNA – Fossil Records

Comparative Anatomy

• Homologous Structures: –Body parts that have the same general

structure but different functions. –Due to common ancestors adapting to

different environments – Examples: (change in notes)• Human arm, whale fin and bat wing

Comparative Anatomy

• Analogous Structures: –Body parts that have the same function but

do not have a similar structure–Due to similar environments and lifestyles–Not common ancestors – Examples: Insect wings and Bird wings

Comparative Anatomy

• Vestigial Structures – Genetic “Leftovers” – Often smaller in size– Often disused – No longer hold any valuable adaptation for

survival– Suggest structures of common ancestry – Examples: tail bones, human appendix, body hair,

goose bumps, wisdom teeth, hip bones in snakes, etc.

Comparative Embryology

• Embryology–Study of early stages of organism

development. –Embryos of related organisms

develop similarly.

Comparative DNA

• DNA Comparisons– Comparing DNA to determine relationships– The more similar DNA sequences are in

organisms, the more related those organisms are.

– Examples: • Hemoglobin – carries oxygen• Cytochrome C – enzyme involved in cellular

respiration

Fossil Records

• Fossils are the remains of a living thing that have been preserved in rock

• Show changes in organisms over time– Ancestors– Transitional species

• By dating the rock, scientists can tell when the organism was alive.

• Also gives clues to how surroundings have changed over time

• Difficulty: fossil record is incomplete

Fossil Records Cont…

• Rock Layers– Age of fossils can also be determined by the

rock layer in which they are found. – Older rocks are found on the bottom– Younger rocks are found closer to the top

• Mass Extinction– When lots of fossils suddenly disappear– Usually evidence of environmental change• KT extinction (dinosaurs)