cycle 8 Flashcards
Homo Sapiens
homo - genus
sapiens - epithet
what is a species?
what defines a species?
- no universal species concept…
- populations with different traits, populations that successfully mate with each other (not with other populations), populations that don’t exchange genetic material with other populations
ecological species concept
a concept of species in which a species is a set of organisms adapted to a particular set of resources, called a niche, in the environment.
morphological species concept
a set of organisms that look similar to each other and is distinct from other sets
biological species concept
a group of organisms that can successfully interbreed and produce fertile offspring - reproductively isolated
phylogenetic species concept
group of populations with a recent evolutionary history
evolutionary tree
- groups are monophyletic (all descendants from common ancestor)
- Must decide how much evolutionary change defines a group or species
Comparing species concepts
different concepts for delineating species give different answers – it’s not clear cut
Reproductive isolating mechanisms (barriers to gene flow)
- Meet > Mate > Fertilization > Zygote > Development > Offspring Variability
Prezygotic Isolation Mechanisms
-Ecological isolation
-Behavioral Isolation
-Temporal Isolation
Mechanical isolation
-Gametic isolation
Postzygotic Isolation Mechanisms
- Hybrid sterility
- Hybrid breakdown
Ecological isolation
occupy same region, but live-in different habitats
Behavioral Isolation
signals not recognized by another
Temporal Isolation
mate a different times of the year
Mechanical isolation
differences in structures prevent interbreeding
Gametic isolation
gametes not compatible, cannot fertilize
Hybrid sterility
offspring survive but are sterile
Hybrid breakdown
First gen hybrids produce viable gametes/offspring, but second gen offspring have lower fitness, are sterile, or are inviable
Allopatric Speciation
two populations are geographically separated physically - geological barrier that individuals cannot cross.
Secondary contact
when populations interact again after being geographically separated.
Outcome of secondary contact
may resume interbreeding, may become partly/fully reproductively isolated
reproductive isolation
causes interbreeding slowy
fusion
populations interbreed quickly
Hybrid zone
individuals of previously separated populations interbreed
hybrids are…
well adapted to environments outside of hybrid zone, low fitness, at risk of evolution. hybrids are favoured!
Reinforcement
accelerates isolation after secondary contact. promotes evolution of prezygotic isolation
Sympatric speciation
populations are not geographically or environmentally separated. not very common
Polyploidy in plants
changes # of sets of chromosomes. Causes rapid speciation. Eg: diploid parental generation can’t interbreed with their tetraploid offspring. This is because gametes have different # of chromosomes = gametic isolation.
Allopolyploidy in plants
cannot undergo meiosis, chromosomes are too different to pair properly. DNA replicates, but cell wont divide – chromosome doubling. Produces gametes that are not compatible with species A/B individuals, creating new species
speciation
more differences evolve and accumulate, causing populations to diverge further apart
