 Adaptation – describes any trait that enhances an organisms fitness or increases its chance of survival.  While adaptations are products of natural selection, variations within a species are the raw material upon which natural selection acts.

 Exaptation – an adaptation that evolved for one function that could also be used for another purpose. Limbs on a lungfish

 1. Structural (anatomical) Adaptations – these may include external or internal changes within an individual, or even mimicry and cryptic colors can be considered physical.

 2. Physiological adaptations – changes within the function of the organism. Enzymes Chemical defenses  3. Behavioral adaptations – how an organism responds to the environment. Migration courtship

 Is evolution perfect????????

 WHAT IS SPECIATION? The formation of a species (a reproductively compatible population, ie. a population that can interbreed and produce viable offspring)  There are two pathways that lead to new species: transformation vs. divergence pg 708 For species to remain distinct, they must remain reproductively isolated, or prevent breeding between closely related species lines.

 GEOGRAPHIC BARRIERS or ISOLATION  REPRODUCTIVE (Biological ) BARRIERS or ISOLATION Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

 Nature has frequently provided geographical barriers that prevent individuals from interbreeding.  Given sufficient time and generations new species may emerge.

 Even when individuals live in the same region factors may exist that prevent interbreeding: Pre-zygotic Barriers – impede the mating process or prevent the egg from becoming fertilized Post-zygotic Barriers – if sperm from one species is capable of fertilizing the egg of another species. There are mechanisms to prevent this hybrid individual from developing.

 Behavioural Isolation – a species may have special signals or rituals that is species specific. Eg. Songs of birds, pheromones etc…  Habitat Isolation – two species can live the same region but occupy different habitats. Eg. Garter snake lives near water where most other snakes prefers open areas.

 Temporal Isolation- species may be isolated due to the time or season they are active or are reproductively viable.  Mechanical Isolation- related species may attempt to mate but are anatomically incompatible.

 Gametic Isolation – even if gametes from different species do meet, rarely will a zygote form. Sperm from one species can not survive in the female reproductive tract of another species.

 Hybrid Inviability – development of the hybrid zygote is stopped at some stage during embryonic development.

 Hybrid Sterility – when two different species can mate but the offspring is sterile. Horse + Donkey = Mule (sterile)  Hybrid Breakdown – when first generation hybrids are viable and fertile but if these hybrids are mated, the next generation are sterile or weak.

 The biological definition of a species does not work in all instances… (discuss)  Other models include: Morphological species concept (physical or phenotype characteristics) Cohesion species concept Ecological species concept Evolutionary species concept