Download Evolution Concepts

Evolution Concepts
Evidence for Evolution
I. Fossils – Physical Remains of Organisms
 Found in Sedimentary
Rock
 Relative Dating –
estimate age by
comparing it to other
fossils.
 Radioactive Dating – Use
of ½ life to determine
age of sample.
II. Anatomical and Physiological similarities
-- Homologous structures
-- implies similar genes
III. Embryological Evidence
-- Similarities in early development
-- implies similar genes
IV. DNA Sequences – All organisms have the same four bases – A, T, C, G
V. Analysis of Amino Acid Sequences with proteins
VI. Geographic distribution of living species – common ancestor
Adaptation – An inherited characteristic that increases an
organism’s chance for survival.
Concept – Organisms with a given adaptation are more
likely to survive and reproduce, their genes will be
passed on to the next generation.
-- This increases the frequency of the gene that caused
the adaptation. In this way, species change over time or
evolve.
-- ORGANISMS THEMSELVES DO NOT EVOLVE
--If an adaptation separates one group within a species from another
group in such a way that they can no longer reproduce, the two
groups may become different enough for scientists to consider them
separate species. This is the process of speciation.
--Dominant alleles do not always lead to an advantage; sometimes
being homozygous recessive for a trait is advantageous.
-- An adaptation which helps an organism in one environment may
not prove to be advantageous in a different environment.
Natural Selection – the process by which organisms that
are better suited to their environment are more likely to
survive and reproduce, thus passing on their gens.
Darwin’s Theory of Natural Selection has four basic principles:
1. Variations exist among individuals in a population.
2. Variations can be inherited.
3. More offspring are produced than can survive.
4. Variations that increase an organism’s chance of
surviving and reproducing are more likely to be passed
on to the next generation.