Earth is thought to be 4.6 billion yearls old with the first living organisms appearing 3.5 billion years ago Man appeared on earth about 2 million years ago. (H. habilis) (Homo sapien = 100,000 years ago)
How did life begin? Evolution – change over time; implies that life began as a single cell and that organisms changed over time
How did life begin? Creationism – God created world and everything in it in 6 days; implies that the organisms present today are the same ones God put on earth
How did life begin? Intelligent Design – states that features of organisms are best explained by an intelligent design rather than an undirected mechanism
Geological Timeline Shows when different life forms originated due to evolution
Proof for Evolution 1.Fossil – any part of a living or once living organism; entire organism, bones of an organism or an impression in a rock a. Extinct – when all organisms of a species are no longer living
Proof for Evolution 2. Comparative Anatomy – study of the structures of organisms; legs of dogs, pigs, sheep, and horses are similar
Proof for Evolution 3. Comparative Embryology – study of the embryos; embryos of chicken, turtle, and rat are similar
Proof for Evolution 4. Comparative Biochemistry – study of the chemicals of life; blood of humans and chimpanzees are similar
Lamarck and Darwin 1.Lamarck - believed in evolution a.Law of Use and Disuse; organisms could change body features during life time i.e. Giraffe change called acquired characteristics b.Inheritance of acquired characteristics – acquired characteristics are passed onto offspring This is not accepted because genetic information can only be passed on to their offspring through sex cells, not body cells
Darwin Voyage of the Beagle: Darwin’s Observations:
Darwin a.Struggle for Existence – based on an essay written by Malths that said the population was growing faster than the food supply; people will suffer and die b.Survival of Fittest – Natural Selection; due to the struggle for existance, only the best, strongest, fastest, etc. will survive
Darwin’s Theory of Natural Selection 1.In nature, there is a tendency for over reproduction. 2.Not all organisms survive 3.Variation exist in all populations 4.Some variations are helpful, some harmful 5.Variations that are suitable for the environment will survive and be passed onto offspring, unsuitable variations will be eliminated 6.Populations as a whole will be better fit for its environment
Gene pool: all of the alleles of the population’s genes
Organisms have adaptations that allow them to better survive Adaptation: an inherited trait which helps organisms survive; starts with a variation. After many generations, all of the organisms have the variation, now called an adaptation o Morphological: structure o Bones of hand, beaks of bird o Physiological: inner working of an organism o Enzymes for digestion, clotting of blood o Behavioral: instinctive reactions to the environment o migration of bird, storing of nuts by squirrels
Evolution of Adaptations Species – group of organisms that breed and produce fertile offspring
Speciation: Evolution of a new species that occurs when members of similar populations can no longer breed and produce fertile offspring because ……….
Geographic isolation: when a physical barrier (lava from volcanic eruptions, sea level changes, etc.) divides a population and each new, smaller population adapts to its own environment creating new species
reproductive isolation: when organisms no longer breed with each other to produce fertile offspring because……….
the genes become too different and fertilization cannot occur
mating times change to different times of the year
one population becomes polyploid (double, triple, etc. of the normal number of chromosomes) because of mistakes in mitosis or meiosis, so they can’t breed with the other population
Divergent evolution: species that once were similar become increasingly different creating biodiversity
Convergent evolution: unrelated species evolve similar traits because they occupy similar environments
Humans did not evolve from chimpanzees. Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human.
Humans are not "higher" or "more evolved" than other living primates. Humans are very good at being humans. Chimpanzees are very good at being chimpanzees. Chimpanzees are NOT less evolved humans. Humans are NOT less evolved chimpanzees.