BIO 1M03 CHAPTER: 1
Biology and the Tree of Life
Organism: Is a life form made of one or more cells and have certain fundamental
• Energy: organisms must acquire and use energy to survive and reproduce.
• Cells : Organisms are made of membrane bound units called cells.
• Information: Organisms process genetic information, encoded in cells (genes),
along with information that they acquire from the environment.
• Replication: An organism must be able to replicate itself.
• Evolution: Organisms are the product of evolution, and their populations continue
• Cell Theory
• Evolution by natural selection
(These key developments are unified by concepts of ancestry and descent. Evolutionary
relationships among individuals, cells, and species are represented by phylogenic trees.)
Cell Theory: All organisms are made of cells and all cells come from preexisting cells.
Multicellular individuals, all cells are descended from a progenitor cell (zygote). This
was made certain over the previously thinking that cells spontaneously generated
themselves. An experiment by Pasteur was conducted with two different shaped flasks
(one curved and one straight). Each flask contained a nutrient mix that could support life.
The curved flask did no grow new cells in the mixture as the new incoming cells were
trapped in the neck of the flask by condensation. This rejected the spontaneous generation
of cells theory.
• This however is not 100% definite. The only cell that was ever
spontaneously generated was the first everliving cell.
• This implicates that we all came from a common ancestor.
In order for natural selection to occur you need:
• (1) variation that is (2) heritable, and (3) influences fitness.
• Darwin and Wallace proposed that all species were related by a common ancestor
and that the characteristics of a species can be modified from generation to
• If these changes improve the organism’s fitness to reproduce these characteristics
will increase in a population over many generations. Increasing the pop. Allele
• Environment also plays a role in natural selection if the new heritable trait is
beneficial in certain environmental conditions.
• Evolution occurs when heritable variation leads to differential success in
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• Species come from other .
• Natural selection acts on individuals, but evolutionary change effects only
Artificial Selection: Driving evolution by artificial means. Altering allele frequency to
human liking to produce desired offspring. This is seen in corn, over many generation of
choosing the sweetest kernels of the cob for crossing has resulted in the corn we eat
• How fast can Artificial selection be? It depends on:
1. How many genes influence the phenotype. More genes mean longer time to shift
2.How much genetic variation exists in the genes.
3. How much the phenotype is controlled and influenced by the environment.
• How far can artificial selection go? : It depends on whether the traits are
deleterious and the limits of the available genetic variation. Ex: Big dogs become
so big that they begin to have joint problems and heart problems due to their
selected for size. If you do not start with the genetic basis for the phenotype you
cannot artificially change the phenotype without genetically engineering the
(Both artificial and natural selection can alter the phenotype of an organism over
generations crossing desired visual traits)
The two central unifying ideas of biology:
1. The cell is the fundamental structure of organisms
2. All species are related