Chapter 24 Flashcards
How do species form?
Speciation
What is speciation?
The process by which one species splits into two or more species.
What is the biological species concept?
Defines a species as a group of populations whose members have the potential to interbreed in nature and produces viable, fertile offspring, but do not produce viable fertile offspring with members of other such groups.
Reproductive isolation
The existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable fertile offspring.
What are the two types of barriers that exist in reproductive isolation?
Prezygotic barrierss - barriers that block fertilization from occurring.
Postzygotic barriers - reproductive isolation occurs after the hybrid zygote is formed.
Habitat isolation
Prezygotic barrier/ecological barrier
Species occupy different habitats within the same area and therefore rarely encounter each other.
Example: fly species, Apple maggot fly and blueberry maggot fly never reproduce with one another because they lay their eggs in different fruits.
What is a liger an example of?
Both prezygotic and postzygotic barriers.
Prezygotic, habitat isolation therefore they never reproduce.
Postzygotic when it happens in a zoo the offspring will be infertile.
Temporal isolation
Prezygotic example
Species that breed during different times of the day, season, years.
Example: skunks and frogs mating at different times of season
Behavioral isolation
Prezygotic example
Courtship rituals that attract mates and enable mate recognition.
Example, blue footed booby
The species can identify their own species via their dance, or song,
Mechanical isolation
Prezygotic example
Mating is attempted, but morphological differences prevent a successful completion.
Their junk doesn’t fit together
Gametic isolation
Mating is attempted, but the sperm of one species is unable to fertilize the egg of another species.
Parts fit but the sperm and eggs can’t fertilize
Reduced hybrid viability
Postzygotic example
Zygote forms but either the embryo does not develop or the offspring doesn’t survive in its environment.
Reduced hybrid fertility
Postzygotic example
The hybrid is healthy but is infertile and can not produce offspring.
Example, donkey and a horse make a mule the mule is sterile
Liger also
Hybrid breakdown
Postzygotic example
When a viable fertile hybrid reproduces, but their offspring are feeble and sterile.
Example, rice hybrids that carry to many recessive alleles and produce feeble offspring.
What is the morphological species concept?
Characterizes species by body shape and structure features.
