Species & Speciation Flashcards
w10
1
Q
nomialism
A
only individuals exist, species are man-made constructs
2
Q
Ernst Mayr
A
- lived with tribe in Papua New Guinea
- “These superb woodsmen had 136 names for the 137 sp of birds which I distinguished (confusing only 2 non-descript sp of warblers)”
- ^ powerful evidence that sp exist!!
3
Q
diffs among sp are a reflection that speciation is a process
A
4
Q
phenotypic sp concept
A
- sp are groups of organisms that are more similar phenotypically to 1 another than they are to other groups
- usually measure many traits at once
-> individs that consistently cluster together are classified as a sp
problems:
- how do we decide which diffs (traits) are important?
- geographic races -> so there’s a diff in outward appearance & iindivids they can mate with
- cryptic sp
5
Q
ways to categorise sp
A
- phenotypic sp concept
- ecological sp concept
- biological …
- cladistic …
- recognition …
6
Q
ecological sp concept
A
- sp are groups sharing a common niche
- diffs among sp relate to ecological resources they exploit
- competition causes character displacement
- individs that avoid competition with another group have adv
problems:
- complex life cycles eg. flatworms
- which niche should we focus on?
7
Q
cladistics sp concept
A
- groups of organisms on single branch of a phylogeny
- defines sp through time
problems:
- hard concept to apply in practice (only really useful intellectually)
8
Q
recognition sp concept
A
- sp are groups with common method of mate recognition
- emphasis on sp cohesion
problems:
- need thorough understanding of a sp mate recognition system to use it
9
Q
biological sp concept
(most widely accepted concept)
A
- sp are groups of interbreeding pops that are reproductively isolated from other pops (Mayr, 1963)
- emphasis on what keeps species separate
- sp share a common gene pool
-> this def explains why members of a sp resemble each other
- important concept as it merges taxonomy with genetics
problems?
- what to do with extinct sp? they haven’t got a gene pool!
- clonal organisms -> gene pool isn’t mixing things up like sexua gene pool
10
Q
all sp concepts agree on…
A
- there are barriers to gene exchange between sp (they may be porous)
- sp are ecologically distinct (to large degree)
- sp have distinct character states (to large degree)
- sp have evolved along independent trajectories (to large degree)
11
Q
Gene flow acts to merge sp
so what keeps them apart?
A
12
Q
speciation is a process
A
- smt must happen to restrict gene flow
- smt needs to drive divergence
- reproductive isolation needs to evolve
13
Q
what can cause restriction of gene flow?
A
-
change in chromosome no.
-> polyploidy can result in instant speciation (2-4% of land plants) -
physical barriers
-> dispersal & colonisation (eg. Hawaiian drosophila)
14
Q
eg. of polyploids
A
barbus fish (sexual)
3 separate polyploid speciation events
15
Q
vicariance
A
process by which a physical barrier separates pops
