Theme A - Phylogeny Flashcards
What is phylogeny?
A visual representation of what is believed to be the evolutionary relationship between different organisms
What is a dendrogram?
A phylogenic tree showing evolutionary descent
What is a key aim of a dendrogram/phylogeny?
To show descent in the fewest number of changes/branching events
What does the terminal point on a phylogenic tree represent?
A species - either living (extant) or extinct
What does the branching point (node) on a phylogenic tree represent?
A speciation event, ie. when one species split into two. The node is the last common ancestor of the two following species.
What is a clade?
All the descendants of a common ancestor
What are sister clades?
Clades that come from the same branching point
What is the difference between monophyletic and polyphyletic species?
Monophyletic species occur in the same clade whereas polyphyletic species occur in different clades
What are the two main divisions of insects?
Winged (pterygota) and wingless (apterygota)
How are winged insects divided in two groups?
Depending on where their wings develop:
- externally to body (exopterygota),or
- internally (endopterygota)
What is a key reason for the diversification of insects?
Their different interactions with flowering plants
What is a parasitoid? Give an example.
It behaves like a parasite but is not truly one.
Example: parasite wasp - lays egg on/in immature stage of another insect, which dies.
Give an example of a visual signal used by frogs, and explain why it has evolved.
Foot flagging. Audio signals are ineffective due to the sound of water.
What is speciation?
It occurs when a lineage splits to form two distinct species; and involves the evolution of reproductive barriers so the two no longer interbreed
What does the biological species concept do?
It defines what a species is
What is a species?
Organisms that interbreed (naturally) to produce viable fertile young, that are reproductively isolated from other species
What two types of reproductive barriers can occur?
Pre-zygotic (before mating) and post-zygotic (after mating)
Give three (out of five) examples of pre-zygotic reproductive barriers.
- Ecological/habitat isolation - species occupy different areas geographically so are unlikely to meet
- Seasonal/temporal isolation - mate at different times of year
- Ethological/sexual isolation - not attracted sexually due to difference in behaviour, communication etc
- Mechanical isolation - reproductive organs not compatible
- Gametic isolation - fertilisation fails
Explain the three post-zygotic reproductive barriers.
- Hybrid inviable - egg fertilised but embryo dies
- Hybrid sterile - offspring survives but is sterile
- Hybrid breakdown - offspring survives but the fertility of their offspring is reduced
What is allopatric speciation?
When two species are separated by geographic barriers, and evolve separately to such an extent that they could not longer inter-breed if they did come back together
What is sympatric speciation?
Two species live in same area but do not come into contact, eg. feed on different plants or active at different times of day/night
What is parapatric speciation?
There is a slight overlap in range where interbreeding occurs to form a hybrid, but most of population remains separate
What is polyploidy?
A type of sympatric speciation in which there is double the number of chromosomes due to a failure during meiosis
What is an osmoconformer? And how does this differ to an osmoregulator?
An osmoconformer is a marine creature that does not regulate salinity - it just lives in full strength sea water and internal fluids are in equilibrium with it.
In contrast, an osmoregulator does control the balance of salinity (osmotic pressure & ions in bodily fluids)
How to crabs regulate osmotic pressure?
Water is taken in through the integument and gills, fluid is excreted as urine by the antennal gland
What is the difference between hypo- and hyper-osmotic?
In hypo-osmotic, the internal osmotic pressure is less than the seawater outside;
In hype-osmotic, the internal osmotic pressure is greater (more saline) than the water outside.
What sort of circulatory system do crabs (and other arthropods) have?
They do NOT have a closed circulatory system of blood. Instead there is a open system, with haemolymph fluid surrounding the internal organs.
What is the isosmotic point (ISO)?
Its the point at which the internal and external osmotic pressures balance
What is the term given for water more saline than seawater?
Hypersaline
What can species that are euryhaline do?
Tolerate a wide range of salinity
What is the principle of parsimony?
That species have evolved in the fewest steps, ie. by the simplest route
How does competition oppose species recognition?
Individuals need to be different enough to stand out. If this goes too far, they may not be recognised as same species.
