Speciation

1
Speciation

• Unit 5 Lecture 5

2
Speciation

• Speciation creation of a new species
• could occur when organisms of the same species
  can no longer interbreed in their natural
  environment
• explains how tigers and lions can interbreed but
  are not of the same species not in same
  environment

3
Speciation

• Causes for speciation
• geographic isolation physical separation of
  populations lead to each changing separately

4
Speciation

• Causes for speciation
• reproductive isolation caused by
• fertilization prevention
• creation of sterile hybrids mule/hinny

5
Speciation

• Causes for speciation
• reproductive isolation caused by
• behavioral differences
• nocturnal/diurnal, blooming seasons, mating
  rituals or choices, etc
• simple physical incompatibilities.

6
Change over Time

• Two ways of hypothesized evolutionary change
• gradualism gradual changes microevolution
  which would slowly build to change org.
• believed to be the major form of evolutionary
  change
• transitions are rarely seen in the fossil record

7
Change over Time

• Two ways of hypothesized evolutionary change
• punctuated equilibrium long periods of little
  change followed by short periods of intense
  change
• because of very incomplete fossil record
  according to the theory of gradualism, created by
  Stephen J Gould

8
Comparing Traits

• Comparing organisms from an evolutionary
  viewpoint, they can be said to exhibit
  convergence or divergence.
• Convergent Evolution
• organisms in similar environments have similar
  traits
• makes sense similar adaptations needed to
  function

9
Comparing Traits

• Comparing organisms from an evolutionary
  viewpoint, they can be said to exhibit
  convergence or divergence.
• Convergent Evolution
• organisms which show convergence have analogous
  structures
• analogous structures different structures with
  the same use

10
Comparing Traits

• Comparing organisms from an evolutionary
  viewpoint, they can be said to exhibit
  convergence or divergence.
• Divergent Evolution
• states that organisms which were once closely
  related become less similar over time because of
  geographic or reproductive isolation

11
Comparing Traits

• Comparing organisms from an evolutionary
  viewpoint, they can be said to exhibit
  convergence or divergence.
• Divergent Evolution
• adaptive radiation states that this change
  between species happens in a short amount of time
• believed to occur because of change in location

12
Comparing Traits

• Comparing organisms from an evolutionary
  viewpoint, they can be said to exhibit
  convergence or divergence.
• Divergent Evolution
• homologous structures similar structures have a
  different use
• assumed to be caused by evolutionary ancestry

13
Comparing Traits

• Comparing organisms from an evolutionary
  viewpoint, they can be said to exhibit
  convergence or divergence.
• Divergent Evolution
• homologous structures similar structures have a
  different use
• DNA evidence doesnt always support this theory
• similar structures are sometimes coded for by
  very different genetic information

14
Comparing Traits

• Vestigial Structures multiple definitions
• previously structures which no longer are
  thought to provide any benefit to organisms
• list of nearly 200 useless structures in late
  1800s to almost none now, leading to a re-vamping
  of the definition according to an evolutionary
  standpoint

15
Comparing Traits

• Vestigial Structures multiple definitions
• previously structures which no longer are
  thought to provide any benefit to organisms
• list of nearly 200 useless structures in late
  1800s to almost none now, leading to a re-vamping
  of the definition according to an evolutionary
  standpoint

16
Comparing Traits

• Vestigial Structures multiple definitions
• previously structures which no longer are
  thought to provide any benefit to organisms
• list of nearly 200 useless structures in late
  1800s to almost none now, leading to a re-vamping
  of the definition according to an evolutionary
  standpoint

17
Comparing Traits

• Vestigial Structures multiple definitions
• currently structure which no longer serve in
  their capacity it is assumed that they had
• based off of comparing organs in organisms
  comparing their uses to their hypothesized
  evolutionary ancestors

18
Vestigialor not?

• Appendix breaks down cellulose in plants
• serves as part of the immune system in humans to
  make white blood cells and antibodies to fight
  infection

19
Vestigialor not?

• Coccyx tailbone continues into tail in other
  orgs
• helps anchor muscles so that we can sit and walk
  correctly including the gluteus maximus
• btw humans born with tails do not have tails
  in the sense of typical orgs, they are just
  fleshy growths.

20
Vestigialor not?

• Pineal gland secretes melatonin, an important
  chemical to our sleep/wake cycles what makes you
  feel sleepy

21
Vestigialor not?

• Tonsils part of immune system
• minimizes respiratory infections, produces
  antibodies
• first line of defense

22
Vestigialor not?

• Wings in flightless birds not for flying
• but often used for balance or for sexual selection

23
Vestigialor not?

• Junk DNA does not code for any traits
• found to have important functions in embryonic
  development, possibly for social functions,
  controlling expression of other genes

24
Vestigialor not?

• Eyes in blind cave animals like fish salamanders

25
Vestigialor not?

• Sexual organs in dandelions dandelions
  reproduce asexually
• vegetative reproduction
• seeds are asexually formed too

26
Vestigialor not?

• Wisdom teeth
• human mouths now smaller than those even a few
  hundred years ago

27
Vestigialor not?

• Male nipples certainly dont nurse children
• ALL humans are female during the first six weeks
  of development
• around 6 weeks, certain hormones are dispersed
  which lead to further development of a certain
  sex.

28
Vestigialor not?

• There is no way to scientifically determine the
  uselessness of an organ just that no function has
  been found Darwin agreed.
• As always, science can only work with available
  info and revise as necessary, which again
  stresses what science truly IS the pursuit of
  knowledge about our world.