Evolution

What is a theory?

Scientific Definition of a Theory A scientific theory summarizes a hypothesis or series of hypotheses that have been supported by repeated testing. It is a valid explanation of a phenomenon.

Theory In science a theory is: 1.Explanatory 2.Predictable 3.Testable

Germ Theory Using our three criteria for a theory, let’s see if the existence of germs is a theory.

In science a theory is… 1.Explanatory -A theory explains something Ex. Germ theory explains that microbes can make us sick.

In science a theory is… 2. Predictable -A theory can accurately guess what will occur in an experiment or observation Ex. A certain set of symptoms can be associated with a certain microbe.

In science a theory is… 3. Testable -A theory can tested by experiments or observations -Must be falsifiable Ex. If we wash our hands, spread of microorganisms will be reduced.

Germ Theory Yes, it’s a theory!

Theory of Evolution Using our three criteria for a theory, let’s see if evolution is a theory.

In science a theory is… 1.Explanatory -It explains something Evolution explains how life changes over time.

In science a theory is… 2. Predictable -You can accurately guess what will occur in an experiment or an observation Evolution predicts how species will change over time.

Example: Fossil Record The theory of evolution predicts more complex fossils will be younger than more primitive fossils.

In science a theory is… 3. Testable -You can create experiments to test your hypotheses -Must be falsifiable

Example: Diane Dodd Experiment

Never say: Evolution is just a theory. All of these are theories: Theory of Relativity Big Bang Theory Theory of Plate Tectonics Particle Theory Quantum Theory

Evolution

What is evolution? The scientific theory that describes changes in species over time and their shared ancestry. * Evolution does not explain the origins of life, science has yet to discover that.

Evolution is the unifying theory of biology! It can be applied to all fields of biology.

Influences on Evolution Species change over time (evolution) AND The Earth changes over time (environmental changes) How does the environment influence evolution?

Influences on Evolution DNA is the blueprint for life How does DNA influence evolution? Mutations The source of genetic variation

Types of Mutations Harmful Mutations: – More common than beneficial mutations – Selected against, and have no influence on populations – Eg: ??? The Effects of Mutations

Types of Mutations Beneficial Mutations: – Relatively rare – Favoured by natural selection – Tend to accumulate in populations over time – Eg: opposable thumbs for gripping The Effects of Mutations

Types of Mutations Neutral Mutations: -Provide no benefit -or harm to the -individual -Will not be selected upon if neither beneficial or harmful The Effects of Mutations

It is estimated that with such a large genome, each human may average several mutations With well over seven billion people worldwide, that’s a lot of genetic variability Mutation Rates

Influences on Evolution Selective Breeding -Humans have domesticated many organisms (plants and animals) -Domestication occurs through artificial selection

Selective Breeding Artificial selection – directed breeding in which individuals that exhibit a particular trait are chosen as parents of the next generation

Wild Sea Cabbage Domestication

Limitations of Selective Breeding -Artificial selection can only influence the genes present in the organism -It cannot create mutations -Horticulturalists would love to create a true blue rose, but until the mutation occurs they cannot breed it themselves

Genetically Modified “Blue” Rose

Questions In textbook: PG. 287 #1,3,9 PG. 317 #28