Lektion 1 Flashcards
Introduktion och Evolution
What is common to all living organisms?
Ordered Complexity, growth, reproduction, energy use, Non-equilibrium steady state, Homostasis (mechanisms to maintain internal stability), sensing and evolutionary adaption.
What are the main reasons an animal is the way it is?
Heredity, constance of DNA sequence, physical constraints (ex size and temperature), intergration of parts, adaptations to present enviroment, filing of a niche and adaptations to past enviroments.
How does the mass in an mammal relate to the metabolic rate?
The metabolic rate decreases as the body mass increases.
What does phyla mean?
A taxonomic rank above class and below kingdom. A group of organisms with a certain degree of evolutionary relatedness.
Tree of life: what does topology indicate?
It indicates the relationship
Tree of life: What does the nodes indicate?
They indicate the ancestors.
Tree of life: what does the branch lenght indicate?
It indicates the amount of change/divergence.
What phyla has the highest number of species?
Arthropods
What is a basal group?
The direction of the base of a rooted phylogenetic tree or diagram. (basal is a very relative term)
What is a crown group?
A collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection and all descendants of the most recent common ancestor.
When was the Cambrian explosion?
500 million years ago
When was the 6:th mass extinction?
65 million years ago
When was the separation of humans and chimps?
10 million years ago
what does a cladogram show?
It showns a classification based on presence/absence of features
what is a phylogenetic tree?
It depicts the relationship between organisms and are based on evolutionary events. (topology, ancestors, amount of divergence etc)
What are the main traits previously used for broad animal classification? (not used anymore)
Symmetry (radial vs bilateral), Cephalisation (sense organs ans brain at the fromt), type of gut (blind vs trough-gut), type of cavities (coelome), segmentation and presence of organs.
How are animals classified today?
By molecular phylogenies (based on protein sequences)
What are the two main principles of evolution?
1) Change
- change in DNa sequence
- Modification of developmental programs
- Allometric/quantitative changes
- Gain loss of charachters
2) speciation
Bifurcation in the tree of life
What was Charles darwins revolutionary idea?
Evolutionary change by random variation and natural selection
What is a species?
groups of actually or potentially interbreeding natural populations which are reproductively insolated from other such groups
what are the mechanisms of speciation?
Genetic changes:
- Genetic drift
-Selection
Separation:
- Reproductive isolation
-Geographic isolation
- Invasion of separate niches
What is stabilizing selection?
The population mean stabilizes on a particular non-extreme trait value. EX:
Birds that lays a lot of eggs may result in malnurished chicks
Birds that lay smaller cluthes of eggs may result in no viable offspring.
so a number of eggs that is the mean would be better
What is directional selection?
When one extreme phenotype is favored over both the other extreme phenotype but also the moderate phenotype.
Ex: the moths that went from white and black to just black because of the pollution in england
What is diversifying selection?
When extreme values for a trait are favored over the intermediate values
Ex
original population consist of white bunnies but gray and gray/white bunnies are favored because they blend better in with the enviroment
