What Is Synapomorphy?

Synapomorphy- Is a trait that is found in certain groups of organisms that exists in no others. It is a homologues trait that exists in no others. Some synapomorphy are: lactation and fur in mammals.

Monophyletic group- Consists of an ancestral population, all of its descendants and only those descendants.
Paraphyletic- An evolutionary unit that includes an ancestral population and some, but not all of its descendants. They are not meaningful units in evolution.
Polytomy- Term for internal node that has more than 2 descendants (sister taxa)

Homoplasy- Similarity among organisms of different species due to convergent evolution. Compare with homology. Example: Bird wings versus Bat wings. Both different ancestor, but both have wings.
* Cenozoic * On land angiosperms were the most important plants and mammals were the most important vertebrates.
Adaptive radiation- When a single lineage produces many descendant species that live in a wide diversity of habitats and use a wide array of resources. Example: Hawaiian silverswords and Anolis Lizards. Two mechanisms can trigger adaptive radiations: * Ecological opportunities- Meaning the availability of new or novel types of resources- have driven a wide array of adaptive radiation. * Morphological innovation- One that allowed descendants to live in new areas, exploit new sources of food, or move in new ways- triggered many of the important diversification events in the history of life.
Mass extinction- Refers to the rapid extinction of a large number of lineages scattered throughout the tree of life. It occurs when at least 60 percent of the species preset are wiped out within 1 million years. Background extinction refers to the lower, average rate of extinction observed when a mass extinction is not
Fragmentation of tropical forest – Leads to threat to biodiversity, since populations cut off. Smaller population are easily affected by catastrophic events, such as storms, disease and outbreaks. Small population also leads to inbreeding depression and random loss of alleles, due to genetic drift.

Ch 54
Co-Evolution: A repeating cycle of reciprocal adaptation. * Competition (-/-) Using same resources, lower fitness for both * Consumption (+/-) One organism eats another, raise fitness of one, lower victim fitness * Mutualism (+/+) Both species interact in a way that raises both their fitness * Commensalism (+/0) When one species is benefiting, while the other is unaffected.
Newt develop poison, but snakes develop immunity, newt will keep developing more to fight off the snakes immunity.
Coevolutionary arms race- A repeating cycle of reciprocal adaptations. Plasmodium is a unicellular protest that causes malaria, and people with HLA-B53 proteins lead to better survival, thus the race for a weapon against