Adaptation 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
Types of Adaptations 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????????
Speciation 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.
How to accomplish speciation? GEOGRAPHIC BARRIERS or ISOLATION REPRODUCTIVE (Biological ) BARRIERS or ISOLATION http://evolution.berkeley.edu/evolibrary/home.php Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.
Geographic Isolation Nature has frequently provided geographical barriers that prevent individuals from interbreeding. Given sufficient time and generations new species may emerge.
Biological Barriers 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.
Types of Pre-Zygotic Barriers 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.
Pre- Cont. 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.
Pre- Cont. 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.
Post- Zygotic Barriers 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.
Again Not Perfect 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
How does it occur? PATTERNS OF SPECIATION? Two Modes Of Speication: (Pg. 714) 1. Sympatric Speciation: when reproductive isolation happens when species are not geographically isolated. 2. Allopatric Speciation (geographical speciation): when speciation happens in species that are geographically separated. GRADUALISM PUNCTUATED EQUILIBRIUM Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.
Adaptive Radiation The creation of new species that have radiated from a common ancestral species that have adapted differently to their various environments. DIVERGENT EVOLUTION and CONVERGENT EVOLUTION Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.
Divergent Evolution The Pattern of evolution where species that were once similar to an ancestral species diverge, or become increasingly distinct.
ADAPTIVE RADIATION AN EXAMPLE OF DIVERGENT EVOLUTION http://evolution.berkeley.edu/evolibrary/home.php http://www.vanderbilt.edu/ans/english/clayton/galapago_finches.gif Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.
Convergent Evolution Similar traits arise independently in species to adapt and survive in similar environmental conditions. They DO NOT share a common ancestor.
CONVERGENT EVOLUTION WHAT IS AN EXAMPLE? http://evolution.berkeley.edu/evolibrary/home.php Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.
Comparing the anatomy of organisms indicates a common ancestry because of: homologous structures - structures having a common ancestry but with different uses in various species. Eg. Similar bone structure of the forelimb of a bat, whale, horse and human suggests these different species have a similar evolutionary origin. Page 113,114 & 664
- analogous structures - body parts of organisms that do not have a common evolutionary origin but perform similar functions. Eg. insect wings and bird wings are similar in function but not in structure. Page 665
- vestigial organs - small or incomplete organs ( or bones ) that have no apparent function in one organism but do have a function in another species. This indicates evolutionary origin from a common ancestor. Page 665 Eg. Human ear muscles, Human appendix, Hip bones in whales, Human tail bone, Leg bones in snakes, and Forelimbs in the flightless ostrich
Co-Evolution the evolution of species together so that both find ways to adapt and survive.