L7 - Macroevolution Flashcards
What is co-speciation? and when does it occur?
If association between two species is very close, cospeciation can occur. Especially likely between parasites and their hosts
What is an example of co-speciation?
Imagine a species of louse living on a species of gopher. When gophers get together to mate, the lice get an opportunity to switch gophers and perhaps mate with lice on another gopher. Gopher-switching allows genes to flow through the louse species
What can prevent co-speciation?
Geographic isolation, causes species to become reproductively isolated, and hence, separate species
What is a phylogeny?
BY studying inherited species’ characteristics and other historical evidence, we can construct evolutionary relationships and represent them on a family tree.
What is shown on a phylogeny when a lineage splits?
Branching, when a speciation event occurs, a single ancestral lineage gives rise to two or more daughter lineages.
What are Clades?
Are nested within one another in a phylogeny tree. They form a nested hierarchy
What is a Clade? pt 2
A grouping that includes a common ancestor and all the descendents of that ancestor.
Using a phylogeny how can you tell if a group of lineages forms a clade?
Imagine clipping a single branch off the phylogeny - all of the organisms on that pruned branch make up a clade
What do phylogenies do?
They trace patterns of shared ancestry between lineages. Each lineage has a part of its history that is unique to it alone and parts that are shared with other lineages. Similarly, each lineage has ancestors that are unique to that lineage and ancestors that are shared with other lineages - common ancestors.
What are phylogeny…?
Trees not ladders, evolution is not progressive
What are some points that cause the most problems when it comes to human evolution?
Humans did not evolve from chimpanzees, humans and chimpanzees share a recent common ancestor that was neither chimpanzee nor human. Humans are not ‘higher’ or more evolved’ than other living lineages. Since our lineages split, humans and chimpanzees have each evolved traits unique to their own lineages
How to read a tree?
The phylogenetic classification system names only clades - groups of organisms that are all descended from a common ancestor. That means reptile is not a valid phylogenetic grouping or we have to start thinking of birds as reptiles. Birds are, in fact, dinosaurs (part of the clade Dinosauria.
What are Homologies and Analogies?
Bird and bat wings are analogous - that is, they have separate evolutionary origins, but are superficially similar because they have both experienced natural selection that shaped them to play a key role in flight. Analogies are the result of convergent evolution.
How to use a tree?
Primate species : sexual selection. Females likely to copulate with >1 partner per estrus. Females mate with only 1 male. When applied to comparative data, conventional statistical methods assume, in effect, that all species are completely unrelated. Most comparative studies will involve species that have descended in a hierarchical fashion from common ancestors
Using trees for species conservation?
If forced to choose, which group of species would you prefer to protect. Species marked in blue or orange. Species in orange are spread out over the tree and species in blue are close-knit clade.
Using trees to see evolution of venom?
One small clade on the fish tree of life. You can see that venom has evolved multiple times. Yielded several important drugs.
Using trees for evolution of behavioural traits?
Male infanticide has been reported for about half of all species in our sample and seems to have evolved independently multiple times. It mostly occurs in social species, less solitary species and least in monogamous species. Male infanticide occurs in species in which social groups contain more females per male, dominant males obtain a higher share of reproduction in a given season, maintain their dominant position for shorter periods.
What is macroevolution?
Evolution on a grand scale - what we see when we look at the over-arching history of life : stability, change, lineages arising, and extinction.
What is macroevolution? pt 2
Grand trends and transformations in evolution, such as the origin of mammals and the radiation of flowering plants. Macroevolutionary patterns are generally what we see when we look at the large-scake history of life. It is not necessarily easy to ‘see’ macroevolutionary ; there are no firsthand accounts to read. Instead, we reconstruct the history of life using all available evidence : geology, fossils, and living organisms.
What are some patterns in macroevolution? 1
Stasis - many lineages on the tree of life exhibit stasis, which just means that they don’t change for a long time. In fact, some lineages have changed so little for such a long time that they are often called living fossils. The coelacanths. A fish lineage that branched off of the tree near the base of the vertebrate clade. It was thought that coelacanth went extinct. But in 1938, scientists discovered a living coelacanth in the indian ocean that looked very similar to its fossil ancestors. Hence, the coelacanth lineage exhibits about about 80 million years worth of morphological stasis.
What are some patterns in macroevolution? 2
Character change, lineages can change quickly or slowly. Lineage A changes rapid but in no particular direction. Lineage B shows slower, directional change. Trilobites, animals in the same animal clade as modern insects and crustaceans, lived over 300 million years ago. Their fossil record clearly suggests that several lineages underwent similar increases in segment number over the course of millions of years
What are some patterns in macroevolution? 3
Lineage splitting (or speciation). Clade A has undergone unusually frequent lineage-splitting, generating a ‘bushy’ tuft of branches on the tree, Clade B has an unsually low rate of lineage-splitting, represented by a long branch with very few twigs coming off. Clade C has experienced a burst of lineage-splitting at the same time.
