Unit 3 - Evolution Notes
Evolution involves change over time....from a biology standpoint evolution looks at how organisms change over long periods of time over many generations and hundreds of thousands of years.
Source of Genetic Change
Mutations are the source of genetic change
* Neutral mutations - do not seem to benefit or harm the organism * Harmful mutations - negatively affect the life of organisms * Beneficial mutations - positively affect the life of organisms
Many species of plant and animal have been domesticated meaning that humans bring them into their homes or near to where they live. Humans have been involved in selecting traits that are desirable and only breeding those plants or animals with desirable traits into future generations.
Ex - Wolves have been domesticated into many different breeds of dog Wild Sea Cabbage has been bred into brussel sprouts, cabbage, cauliflower and broccoli!
Dimitri Belyaev - did an experiment with the silver and red fox. He selected only foxes that have the trait of being tame. After 35 generations (within his lifetime), he was able to breed tameness into 80% of the offspring. They became very dog like and even changed appearance to be more dog like.
Problems with artificial selection
* Breeders may favour traits that lead to less genetic diversity * Some dogs have bad hips
* Sweet corn is prone to insect damage
Leading to Evolution
* French scientist – Buffon wondered about anatomical features that served no purpose * Life must change over time he thought (from perfect to different)...not true but interesting
* Lamarck proposed two principles
* Use and it gets stronger, disuse and it gets weaker (ex...Giraffes stretch their necks to get food...their necks get longer) * The inheritance of acquired characteristics (ex...future generations of Giraffes pass along their longer necks to offspring)...this is not true but does lead to thinking about evolution Evidence of Change in Fossils
Fossils are loosely defined as being over ten thousand years or older Reading Fossils
* Many fossils appear to be of unusual and unknown organisms...thousands of species are no longer living * No fossils or most living species
* Fossils are deep within rock formations...some 1 km below Earth’s surface * Fossils are found in unexpected locations...sea life in mountains and deserts? * continued
* Fossils of simple organisms are found in all depths
* Fossils of more complex organisms are only at shallow depths * Fossils at shallow depths more likely resemble living species * Rock layers contain fossils of many species that do not occur in layers above or below them
* Charles Lyell – father of Modern Geology
* Earth has been changed by the same processes in the past that are occuring in the present * Geological change is slow and gradual rather than fast and catastrophic * Natural laws that influence these changes are constant and eternal, and they operated in the past with the same intensity as they do today * EARTH IS EXTREMELY OLD and LIFE HAD A LONG TIME TO EVOLVE ...this was radical thinking back in 1830!!
The Origin of Species (1859)
There are two main points that Charles Darwin had to his theory on the Origin of the Species
* descent with modification
* all organisms related through descent from some unknown prototype that lived in the remote past * habitat influence accumulation of adaptations for specific ways of life
Natural Selection and Adaptation
Signs Of Evolution
* geographical distribution of species
* succession of forms
* descent from common ancestors
Homologous versus Analogous features
* homologous - structures share a common origin but serve different functions in...
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