Transcript Applied Biology 15.1 Origins of Biological Diversity ppt

Origins of Biological
Diversity
Chapter 15: pp 322-351
Concept 15.1
The origin of new species.
 Essential question:
 How do biologists identify species?
 How do species arise?
 Objectives:
 Explain biological species concept.
 Compare microevolution and macroevolution.
 Describe types of reproductive barriers.
 Analyze how adaptive radiation contributes to
species diversity.
What is a species?
 A distinct form of life.
 Biologists use the biological species concept
to define a species as a population whose
members breed with one another to produce
fertile offspring.
 Members of one species do not breed with
members of another species.
 This definition- for sexually reproducing
organisms.
How does macroevolution differ from
microevolution?
 Microevolution is evolution on the smallest
scale; generation to generation change in the
allele frequencies in a population.
 Macroevolution is dramatic changes that are
seen in the fossil record. To explain how we
evolved from simpler life forms. Includes:
 Origin
of different species- speciation.
 Extinction of species.
 Evolution of major features
Key concept- New species leads to
biodiversity
Figure 15-2 Branching or cladogenic evolution.
If one species evolves into two or more surviving species, diversity increases.
Reproductive Barriers:
 Reproductive isolation- keeps 2 similar
species from breeding. Due to:
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Timing- different breeding seasons. Skunk
example.
Behavior- different courtship/mating. Ex.
Songs of birds
Habitat- adapted to different habitats- Fish ex.
 Incompatible reproductive structures.
 Infertile hybrids- Horse x Donkey
mule.
Geographic Isolation separates populations leading
to new species.
 Examples include:
 mountain ranges- range of ecological zones.
 Glaciers and isolated islands
 Depends on the organisms’ ability to move about.
Examples:deep canyons,wide rivers. Birds, pollen,
coyotes vs. antelope squirrels.
 Splinter populations-separation of a small portion of
the population from the main population.
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Crucial event in origin of a new species.
Genetic drift- chance and Natural selection can make
the splinter population less and less like the main
population.
Do all isolated populations survive
and become new species?
 No , not all isolated populations survive and
become new species.
 Speciation only occurs if the two populations
can no longer interbreed Not all isolated
populations survive and become new
species. with each other.
 Figure 15.6 model- pg 328.
Adaptive Radiation
 Evolution from a common ancestor that
results in diverse species adapted to
different environments.
 Transparency- Figure 15-7 pg. 328.
 Islands serve as showcase- ex. Hawaiian
islands.
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Physically diverse with differences in altitude
and rainfall .
New lava flow supports adaptive radiation.
Most native species are found nowhere else.
Tempo of Speciation
 Punctuated equilibrium- a model used to
address the observation that species often
diverge in spurts of rapid change, then exist for
long periods of time with little change.
 The refining of a scientific theory of gradual
change.
 Natural selection and adaptation happen, but
when the species is “young” .
 Major changes are less common once the
species is established.
 Speciation is rapid in terms of the fossil record.
 Most successful species last 1-5 million years.
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 Figure 15-9
In contrast to a more gradual model of evolution,
punctuated equilibrium suggests that a new species
changes most as it buds from a parent species. There is
little change for the rest of the time the species exists.