Adaptations = Any trait or behavior that helps an organism ...
Adaptation – describes any trait that enhances an organisms fitness or increases its chance of...
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Transcript of Adaptation – describes any trait that enhances an organisms fitness or increases its chance of...
![Page 1: Adaptation – describes any trait that enhances an organisms fitness or increases its chance of survival. While adaptations are products of natural.](https://reader038.fdocuments.in/reader038/viewer/2022110403/56649e745503460f94b74546/html5/thumbnails/1.jpg)
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.
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Exaptation – an adaptation that evolved for one function that could also be used for another purpose.
Limbs on a lungfish
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1. Structural (anatomical) Adaptations – these may include external or internal changes within an individual, or even mimicry and cryptic colors can be considered physical.
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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
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Is evolution perfect????????
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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.
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GEOGRAPHIC BARRIERS or ISOLATIONGEOGRAPHIC BARRIERS or ISOLATION REPRODUCTIVE (Biological ) BARRIERS or ISOLATIONREPRODUCTIVE (Biological ) BARRIERS or ISOLATION
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.
http://evolution.berkeley.edu/evolibrary/home.php
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Nature has frequently provided geographical barriers that prevent individuals from interbreeding.
Given sufficient time and generations new species may emerge.
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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.
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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.
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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.
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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.
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Hybrid Inviability – development of the hybrid zygote is stopped at some stage during embryonic development.
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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.
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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