Download How Populations Evolve

Evolution
Website: http://evolution.berkeley.edu/
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Define the concept of evolution and explain what evolution is and what is not
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Explain how natural selection is more a process of editing than a creative
mechanism.
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Explain why a population is the smallest unit of evolution and not the individual
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Describe and distinguished each of the mechanisms of evolution
•
Distinguish between microevolution and macroevolution
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Describe the structure and function of plant organs: stems, leaves and roots
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Describe the function of the different types of tissues: dermal, vascular, ground
Evolution is the explanation of many facts of life
FACTS:
Life has change through time
• Extinction is common
• Species exist today that did not exist before
Today’s species share many features
• Similar DNA and proteins
• Same genetic code
SCIENTIFIC EXPLANATION:
Descent with modification
(theory of evolution)
Independent lines of evidence to support it:
Misconceptions about Evolution
Biology professor interviewed in Colbert Report
Evolution is NOT in conflict with any religion
Evolution, as science, looks for natural explanations to natural phenomena
Evolution: descent with modification
Evolution can take place at many different levels
within a species (microevolution)
and
above the species level (macroevolution)
Microevolution:
descent with modification within a population
POPULATION is a group of organisms that interbreed with each other
1st generation
What has been modified?
2nd generation
Proportion of the phenotypes in the population has changed over time
These phenotypes have a genetic basis
At the population level,
evolution is a change in the proportion of alleles over time
But why did this change happen?
What are the mechanisms (causes) of change?
What was the cause for the change in this population?
Mechanism: ____________
A rare change in the DNA of a gene introducing a new allele
What was the cause for the change in this population?
Mechanism: __________
Transfer of alleles between two populations
What was the cause for the change in this population?
Mechanism: _____________
Changes in the gene pool of a small population due to chance.
What was the cause for the change in
the population?
This type of trait is said to be an adaptation
CLOSER LOOK AT GENETIC DRIFT AND
NATURAL SELECTION
All of the mechanisms cause changes in the
proportion of alleles in a population
But
Only natural selection and genetic drift
CAN NOT happen unless
there is genetic variation present
Species that have been endangered and
rebound show low genetic diversity
Hundreds of thousands of Elephant seals
once inhabited the Pacific Ocean.
The Northern population were slaughtered in the 1800s
for their blubber
By 1892, only 50 to 100 individuals were left.
1900 the Mexican and US government decided to protect them
Today, there are approximately 160,000 northern elephant seals.
The Northern population of elephant seals
is less genetically diverse than the Southern Population.
What type of mechanism is this?
Angiosperms are subdivided into Monocots and Dicots
Plant structure
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Plants, like animals, have
organs composed of different
tissues,
which are composed of cells.
•
Tissue is group of cells with a
common function and
structure
•
Organ consists of several
types of tissues that carry out
a particular function
Roots
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Function:
Anchors plant in the soil,
absorbs and transports minerals and water,
stores food.
•
Monocot roots
consists of a mat of generally thin roots
spread out shallowly in the soil.
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Dicots have one main vertical taproot
with many small secondary lateral roots
growing outward.
Stems
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Function:
Support the leaves and flowers.
Green stems also perform photosynthesis
.
The buds are undeveloped shoots.
Leaves
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Function: photosynthesis
It is has a large surface area to maximize light harvesting
They are thin so that light will penetrate through to the bottom cells
Monocots have parallel venation
Dicots have branched venation
The three types of tissues: dermal, vascular and ground
•
Each tissue is continuous
throughout the plant
From root to stem to leaf
•
But,
Are there differences in the tissue
arrangement between stems
and roots?
Are there differences in the tissue
arrangement between monocots
And dicots?
Specializations of dermal tissue:
Stems and leaves: secrete waxy
coating (cuticle)
Leaves have special cells:
guard cells which
regulate the size of the stomata
Roots: cells with root hairs
Function?
Vascular tissue transports materials and supports
• Xylem:
Transports water and dissolved minerals and it is reinforced by
lignin (wood) for added support)
• Phloem:
Transports organic nutrients (sugars)
The arrangement of the vascular tissue
varies depending on the organ
And between monocots and dicots.
Root:
Stems:
leaves:
Ground tissue fills the area between epidermis and
vascular tissue
Ground tissue in leaves
is called the mesophyll
Function?
Ground tissue in stem
Called pith or cortex
Function?
Ground tissue in roots
also called cortex
Function?
Internal structure of a leaf
Upper and Lower Epidermis:
protective function
lower epidermis generally contains
more stomata
Epidermal cells lack chloroplasts
Palisade Mesophyll : tightly packed cells on the upper surface
Contain three to five times as many chloroplasts as
those of the spongy parenchyma.
Chloroplasts remain usually near the cell wall,
since this adjustment guarantees optimal use of light
Spongy Mesophyll : loosely arranged cells
Creates air spaces to facilitate gas exchange
Ex 12. Part IV
• Procedure 8: fill out table
• Procedure 9: stomata, sketch in page 101
• Procedure 11: prepare slide of leaf, sketch
in page 101