Adaptation and Speciation - PowerPoint PPT Presentation

Loading...

PPT – Adaptation and Speciation PowerPoint presentation | free to download - id: 7e0c60-YTdmN



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Adaptation and Speciation

Description:

Adaptation and Speciation SBI 3U – PowerPoint PPT presentation

Number of Views:125
Avg rating:3.0/5.0
Slides: 35
Provided by: AaronP153
Learn more at: http://mail.rsgc.on.ca
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Adaptation and Speciation


1
Adaptation and Speciation
  • SBI 3U

2
Adaptation
  • Any trait that increases an organisms chance of
    survival and probability of successful
    reproduction
  • A product of natural selection
  • Organisms become adapted to their environment
    over a period of time through natural selection
  • Variations within a species are the raw material
    upon which natural selection acts

3
Types of Adaptations
  • 1. Structural Adaptation - physical features on
    an organism
  • Anatomical - shape and arrangement of features
  • Ex. Teeth in carnivores, vascular tissue in
    plants
  • Mimicry
  • Enables one species to resemble another species
    or part of another species
  • Ex. Fly that resembles a yellow-jacket wasp
  • Cryptic Colouration
  • Makes potential prey difficult to spot
  • Ex. Camouflage

4

Mimicry
  • A palatable
  • or harmless
  • species
  • mimics an unpalatable
  • or harmful
  • model

5
Cryptic Colouration
6
Types of Adaptations cont
  • 2. Physiological Adaptations
  • Associated with functions in organisms
  • Ex. Enzymes for blood clotting
  • Ex. Proteins in spiders silk
  • Ex. Chemical defense in plants
  • Ex. Ability of bacteria to withstand heat

7
Types of Adaptations cont
  • 3. Behavioural Adaptations
  • How organisms respond to their environment
  • Ex. Migration
  • Ex. Courtship displays
  • Ex. Foraging behaviour
  • Ex. Response of plants to light

8
How Species Form
  • Scientist must consider the following when
    distinguishing one species from another
  • Physiology
  • Biochemistry
  • Behaviour
  • Genetics

9
Biological Species
  • Most common definition of species
  • - a species consists of a reproductively
    compatible population
  • - a population that can interbreed and produce
    viable and fertile offspring
  • Note Not always possible to apply this definition

10
Forming New Species
  • Speciation
  • formation of a new species from an existing
    species
  • Macroevolution

11
  • Two general pathways
  • Transformation
  • - results from accumulated changes over long
    periods of time such that one species is
    transformed into another
  • - also called Phyletic Speciation

12
(No Transcript)
13
  • 2. Divergent Speciation
  • One or more species arise from a parent species
    that continues to exist
  • Promotes biological diversity
  • increases number of species

14
(No Transcript)
15
Support for both concepts suggests that a
compromise or a combination of the two models
works to produce new species
16
Barriers to Reproduction
  • Geographical Barriers
  • Keeps populations physically separated
  • Ex. Rivers
  • Biological Barriers
  • Keeps species reproductively isolated when their
    habitats overlap

17
Biological Barriers
  • Pre-zygotic Barriers - prevent mating or
    fertilization
  • Post-zygotic Barriers - prevent hybrid zygote
    from developing into a healthy fertile adult

18
Prezygotic Barriers
  • 1. Habitat Isolation
  • 2. Behavioural Isolation
  • 3. Temporal Isolation
  • 4. Mechanical Isolation
  • 5. Gametic Isolation

19
Habitat Isolation
  • Populations live in different habitats or
    ecological niches.
  • Ex mountains vs lowlands.

20
Behavioral Isolation
  • Mating or courtship behaviors different.
  • Different sexual attractions operating.
  • Ex songs and dances in birds.

21
Temporal Isolation
  • Breeding seasons or time of day different.
  • Ex flowers open in morning or evening.

22
Mechanical Isolation
  • Structural differences that prevent gamete
    transfer.
  • Ex anthers not positioned to put pollen on a
    bee, but will put pollen on a bird.

23
Gametic Isolation
  • Gametes fail to attract each other and fuse.
  • Ex chemical markers on egg and sperm fail to
    match.
  • Separates certain closely related species of
    aquatic snails

24
Post-Zygotic Barriers
  • 1. Hybrid Inviability
  • Hybrid offspring are unlikely to live long
  • Ex. Hybrid from sheep and goat die in early
    development
  • 2. Hybrid Sterility
  • Offspring of genetically dissimilar parents are
    likely to be strong but sterile
  • Ex. Horse Donkey Mule

25
  • 3. Hybrid Breakdown
  • First generation of hybrids are viable and
    fertile
  • When hybrids mate the offspring of the next
    generation are sterile or weak
  • Ex. Cotton

26
Types of Speciation
  • I. Allopatric Speciation
  • - When a population is split into two or more
    isolated groups by a geographical barrier
  • - Sometimes called geographical speciation
  • - Eventually the groups will become so distinct
    that interbreeding will be impossible
  • - Isolation does not need to be indefinite, but
    it does need to be long enough for population to
    become reproductively incompatible
  • Ex. Glacier, lava flow, ocean levels

27
(No Transcript)
28
Adaptive Radiation
  • This is a form of allopatric speciation where a
    common ancestral species diversifies into a
    variety of differently adapted species
  • Ex. Darwins Finches

29
Darwins Finches
30
  • II. Sympatric Speciation
  • -When populations live in the same geographical
    area become reproductively isolated
  • -More common in plants than animals
  • -Speciation can occur in 1 generation if genetic
    change results from parent to offspring
  • Ex. Extra chromosome (called polyploidy)
    usually in plants which can self pollinate

31
(No Transcript)
32
Convergent vs. Divergent Evolution
  • Divergent Evolution - a pattern of evolution in
    which species that were once similar to an
    ancestral species diverge, or become increasingly
    distinct (finches)
  • Convergent Evolution - similar traits arise
    because each species has independently adapted to
    similar environmental conditions, not because
    they share a common ancestor (ex. birds and bats)

33
The Pace of Evolution - 2 Hypotheses
  • Gradualism
  • Changes occur slowly and steadily before and
    after a divergence
  • Big changes accumulation of many small changes
  • Fossil record doesnt support this hypothesis
    well
  • Fossil record shows species appearing suddenly

34
  • Punctuated Equilibrium
  • (Gould and Eldredge 1972)
  • History consist of long periods stasis (no
    change) interrupted by periods of divergence
  • Most species undergo major change when they first
    diverge from parent species
  • Fossil records support this theory
About PowerShow.com