J. DeVore

 Analyze the conceptual model that Darwin uses to explain the divergence of species (the "tree of life"). How does this model help explain the relatedness and diversity of species?

The tree of life helps model the diversity of life in that each period of newly growing trees is divided into branches that kill all of the overcrowded and old or dead branches just as newer species have beaten older species in life. The branches that go into different directions are all part of different families of species and they become diverse. Older branches have new branches as their descendants just as older species have newer species as their descendants. Most past species have died out and left no descendants just as branches have died out and have no more leaves or off branches. Most of the earlier branches have died and fell to the ground and some are now fossilized, just as most past species died and now only exist as fossil. Sometimes multiple branches are entwined with each other just as old species are sort of interbred together and the branches might survive if they are in a lucky part of the tree just as old species if they are in a lucky part of the Earth. The new branches replace old weaker branches just as old weaker species are replaced by new species that are stronger and take over. 

Discuss the importance of variability and inheritance in Darwin's theory of evolution. How do these concepts relate to the formation of new species and the adaptation of organisms to their environments?

Species have to inherit their genes. If any inherited genes help the species to survive then the genes are likely to be reproduced and thrive. Traits that are inherited include, for example, the color of the eggs from the chickens or the caterpillar in the cocoon stage. Natural selection is just like human selection by letting the natural traits that help species survive and reproduce a lot. Meanwhile species that don’t inherit the traits get eliminated. Species have inherited traits from lots of ancestors and this helps species develop more thoroughly. Traits can only be inherited by only males or only females and traits in one or the other sex can help the species survive. Variability comes from the conditions in which the species live and from using traits in order to survive. Variability can be very small to help a species survive better. Variability can either come from a large population or a smaller population that is diverse as long as those variations can be inherited by some of the offspring. If species are around for a long time the species tend to have a lot of variation. Variability and inheritance create new species in different environments over a long time.