form and function Flashcards
why do insects have six legs
stability, points of contact in climbing, climbing in a fractal world
what is natural selection
the process whereby organisms better adapted to their environment tend to survive and produce more offspring.
what is evolution
Over time selection produces genes that increase fitness in particular environments
what is an adaptation of a butterfly
- butterfly proboscis- for feeding on tubular flowers
- wings for flight
what are the coconut crabs adaptations
the claws
what are the questions to test for an adaptation
- is the trait heritable
- is it functional
- does the trait increase fitness
- evolutionary history can help
what are non adaptive explanations for traits
- chance events
- by product of another characteristic
- biophysical constraint or default arrangement
- they could be a product of genetic drift
what are some of the features of body plans in invertebrates phyla ?
skeletons
symmetry
segmentation
body cavities
what is the trade off theory
This theory suggests that you can’t as an organism be good at everything all of the time. The range in the diversity of the invertebrate forms reflect the diversity of life styles
what are the trade off in shell morphology
in freshwater snails if they are round they are crush resistant however they are more susceptible to the entry of predators. Elongate shape is more resistant to predators but they are more likely to be crushed.
what does the cross sectional area in worms determine ?
determines the resistance to burrowing. Being long and thin is a win as they are low resistance and they have opportunities to have a high pushing strengths and they can have lots of legs and muscles.
what is the Reynolds number?
Re: the ratio of inertial to viscous forces in fluid. When re is high we tend to see turbulent flow but when it is low the fluid motion is more smooth or laminar
Re=?
length X relative fluid velocity / viscosity
what is the outcome of evolution
- diversity of organisms
- over 99% already extinct
- organised ways of organising and classifying
what is taxonomy
the scientific study of naming, defining and classifying groups
what is phylogeny
study of the history and relationship between organisms
what is the Linnaean system- hierarchical classification
- Genera contained within families
- Taxon is the taxonomic unit at any level of the hierarchy
- Genera and species name always written in italics
- Higher taxa have capitals, Latin binomials are comprised of genus and species name
what does the Linnaean system consist of
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
what are clades
ancestral species and all its decedents
how are clades nested
Clades can be nested within larger clades
what is a taxon
equivalent to a clade if its monophyletic ( a group composed of the most common recent ancestor and all of the recent descends of it)
what are phylogenies made up of
Made up of branches and nodes
what does polytomy mean?
more than 2 lineages diverge from a single nodes
what are sister taxa
share and immediate common ancestor
what is a Monophyletic group
ancestorial species and all its decedents
what is a Paraphyletic group
ancestorial species and some of its decedents
what is a Polyphyletic group
taxa with different ancestors
what is convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time.
Appear similar but will have different internal anatomy and physiology
why is molecular data important when it comes to phylogenies
Molecular data can revise phylogenies and provider a deeper understanding
What phylogenetic trees do not tell us:
- Sequence of branching does not indicate age
- If trees are based on morphology/ anatomy the branch lengths do not indicate time
- Cannot assume a taxon evolved from the taxon next to it e.g. humans did not evolved from chimps
what are molecular clocks
means of dating the divergence of organisms by looking at the changes in the structure of basic proteins or DNA
what are the assumptions about mutations
- they accumulate randomly
- the number of changes is proportional to time since divergence from the common ancestor
how are molecular clocks calibrated
by measuring the differences between the genes in different groups that diverged at a known point (using fossils or geological data)
what are the problems with molecular clocks
- Regularity of change over time thought to be due to genetic drift. This is a random accumulation of mutations with little effect on fitness
- Only ticks regularly for mutations that are neutral
- DNA regions under strong neutral selections are not neutral and not good for phylogenies
- Clock rate can vary between taxa and different regions of trees
