What does heritable mean
- it means that the trait is part of an organisms’s genetic code
- > and therefore has a chance to be copied to the organisms’s offspring
- > heritability is the reason that sons and daughters tend to resemble their parents
-note a trait must be heritable for the trait to evolve
Are traits always copied from parents
- no they can be new
- >eg; random genetic mutation
Does variation have to exist for selection to occur for a given trait
-yes
What are the four charactarestics of evolution
1) Heritable
2) Variation
3) Advantage or differential success
4) Competition
Does the evolution of anew species mean the extinction of an ancestor
- not necessarily
- > for instance, a new species might simply branch off from an ancestral species if only a single population of the ancestral species was exposed to new environmental conditions that favored new traits
- > the population in the new environment would acquire new traits better adapted to the environment
- > the ancestral species might continue to exist in its ancestral environment
How are organisms grouped based on evolution
- they are grouped together based on their most recent shared common ancestors
- > eg; hadrosaurs, ceratopsians, ankylasours, stegosaurs, and pachycephalosaurs belong to the group ornithischia
Where did dinosaurs evolve from
-they evolved from a single species of amniote tetrapod
What is a character
- it is a derived heritable trait that can be described and labeled
- > a shared derived character is present in two or more groups and their common ancestor
- > but it is not present in any more distantly related groups
eg; tooth shape, bipedal or quadrupedal, number of holes behind the eye in the skull
- the differences in the anatomical features are called characters
- > eg; the spines of Spinosaurus might be long in comparison to other species
Is a shared derived character called synapomorphy
- yes
- > for instance, all species of ornithiscians have a special bone in the lower jaw that forms a beak(a predentary)
- > no other dinosaurs have this special beak bone
- > this is a synapomorphy that describes the ornithiscians group
- eg; the hip structure of the ceratopsian, ankylasour and hadrosaurs ahre shared derived characteristics
- > the backward facing hip pubic bone
-eg; the frill and pointed beak are each a shared derived character of all ceratopsains
eg; the pachephalosaurs have the thick domed skull
What is convergent evolution
- it is the evolution of similar traits in two different lineages
- > eg; spinosaurus and ouranosaurus(their sails)
- > eg; evolution of wings in flying vertebrates(birds, pterosaurs and bats)
- > birds use feathers, bats have a membrane that goes between all five fingers and pterosaurs had a wing membrane that was supported by just one finger
- eg; bipedalism in birds and humans
- usually convergent evolution results when two lineages must adapt to similar environments and to similar modes of life
What is the concept of parsimony
- it is the idea that all other things being equal
- > the simplest answer is usually the right one
- note Parsimony is also referred to as Occam’s razor
- in evolutionary terms, this means that this is the fewest number of evolutionary changes
Do scientists use computers to determine the evolutionary relationships between a large number of species
- yes
- > these programs analyze a list of characters that is compiled by the researcher
- > this list is referred to as the MATRIX
- based on the character matrix
- > the computer applies a principle of parsimony to arrange the organisms in a sequence of relationships that require fewest instances of convergeng evolution
-the program organizes a phylogenic tree
Describe the characteristics of phylogenic trees
- it is composed of nodes and branches
- a node is where two branches diverge
- > shows a point at which two lineages share a common ancestor
- a group of species that share a common node is a clade
- > clades can be very small or very large
- > there are no size limits
- > a clade must contain the ancestor of a group and all of its descendants
- a group that does not contain all of the descendants of a common ancestor is not a clade
- analyses works best when there are lots and lots of characters
Did Huxley support evolution
- yes
- > he was one of the earliest advocates of the theory of evolution
- > he was also the first sciwntist tor ecognize that birds evolved from dinosaurs
- he also cited that the Archaeopteryx is the missing link between dinosaurs and birds
- > this species has long wing-feathers and tail feathers just like a bird
- > but they also have teeth, clawed fingers and a long series of tail vertebrae like a dinosaur
What is significant about Sinosauropteryx
- it was the first non-avian(non-bird)dinosaur to be discovered with feathers
- > the feathers had a simple structure compared to the feathers of modern birds
- > these feathers are used for insulation, not for flight
What is so special about Yutyrannus
-it is a large tyrannosauroid with feathers
What are the only clade of dinosaurs alive today
- birds are the only clade of dinosaurs alive today
- >birds can be classified as theropod dinosaurs because they evolved from theropod dinosaurs
What is the difference between Aves and Avialae
- Aves refers to all living birds and extinct ones like the dodo and moa
- Avialae is referring to the flying dinosaurs, which includes extinct species that looked very similar to modern birds(including Archaeopteryx)
What is a clade
-a group of species that share a common ancestor
Describe the characteristics of Archaeopteryx
- it had feathers
- it would have been identified as a theropd dinosaur
- > because it had a small skull with sharp serrated teeth
Are feathers a synapomorphy for birds
- no
- >as many dinosaurs had feathers
