Download Vertebrate Zoology

Vertebrate Zoology
Chapter 1
How do we learn from animals?
• Experimentation
* Physiological Science
1. How will a system respond to a disturbance?
2. Create the disturbance
3. Compare observations with expected results
• Comparison
* Evolutionary Science
* Comparative anatomy
* Molecular biology
* Cell biology
* Ecology
Evolution Theories
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Perpetual Change
Common Descent
Multiplication of Species
Gradualism
Natural Selection
Perpetual Change
Living organisms are not constant in
form or function, nor are they
perpetually cycling but always
changing
Proposed in antiquity
Common Descent
• All forms of life descended from a
common ancestor through a branching
of lineages (Phylogeny)
• Supported by DNA & cell structure
Phylogeny
• The history of animal life depicted as a
branching tree
• Earliest animals are placed at the trunk
• Each branch represents a new species
which inherits many traits from the
ancestor but also has a new (DERIVED)
trait which appear for the 1st time
Phylogenetic Tree
Multiplication of Species
• New species arise by the transformation
of old ones
Gradualism
• Differences in anatomical traits within
different species accumulate over long
periods of time
Charles Darwin
(1809-1882)
• Born in England
• Attended medical school,
HATED IT, and dropped out
to become a priest
• Boarded the H.M.S. Beagle
for a 5 year UNPAID
journey as a naturalist
Journey of the H.M.S. Beagle
Alfred Russel Wallace
(1823-1913)
Presented a paper with
identical ideas as Darwin on
July 1, 1858 at the Linnean
Society meeting
Was a botinist who came up
with vitually the same
concept of natural selection
more or less independently
through his studies on the
Malay archipelago. Darwin
panicked because he was not
ready with his book yet!
Where did Darwin and
Wallace get the idea of
evolution?
Jean Baptiste Lamarck
(1744-1829)
• Lamarck claimed that evolution
was driven by "use vs. disuse"
• A used structure will become
larger, stronger and more
important.
• A disused structure will atrophy
and become VESTIGIAL.
Theory of “Use vs Disuse”
• The long necks of
giraffes were due
to their stretching
for food, and
giraffes passed
their stretched
necks on to their
offspring.
• Similarly, the big,
“ripped” muscles
developed by the
village blacksmith with
all his hammering and
slinging of heavy metal
objects would be
expected to be passed
on to his offspring.
Theory of “Acquired
Characteristics”
• Lamarck claimed
that traits
acquired during an
organism's lifetime
could be inherited
by that organism's
offspring.
Georges Cuvier
(1769-1832)
• Created Paleontology
(The study of fossils)
• He noted that deeper
layers of sedimentary rock
had diversity of organisms
far different from present
day life found in more
recent layers
• Proposed the idea of
extinction based on fossils
James Hutton
(1726-1797)
• A Scottish geologist who challenged
Cuvier's view in 1795 with his idea of
GRADUALISM
• Proposed that large changes in the
earth's surface could be caused by slow,
constant processes such as erosion.
Charles Lyell
(1797-1875)
• Earth processes had been going on
constantly, and could explain the
appearance of the earth.
• This theory, uniformitarianism, was
a strong basis for Darwin's later
theory of natural selection.
Thomas Malthus
(1766-1834)
• Suggested that much of humanity's
suffering (disease, famine, homelessness
and war) was the inevitable result of
overpopulation: humans reproduced more
quickly than their food supply could
support them.
• Malthus showed that populations, if
allowed to grow unchecked, increase at a
geometric rate.
Darwin made some profound
observations, from which he inferred
some brilliant conclusions...
• Observation #1. All species have huge potential fertility
• Observation #2. Except for seasonal fluctuations,
populations tend to maintain a stable size.
• Observation #3. Environmental resources are limited.
Inference #1
• The production of more individuals than the
environment can support leads to a "struggle
for existence," with only a fraction of
offspring surviving in each generation.
Observations
• Observation #4: No two individuals in a
population are exactly alike
• Observation #5: Much of the observed
variation in a population is heritable
Inference #2
• Survival in this "struggle for existence is not
random, but depends, in part, on the
hereditary makeup of the survivors.
• Those individuals who inherit characteristics
that allow them to best exploit their
environment are likely to leave more offspring
than individuals who are less well suited to their
environment.
Inference #3
• Unequal reproduction between suited and unsuited
organisms will eventually cause a gradual change in a
population, with characteristics favorable to that
particular environment accumulating over the generations.
SO WHAT IS THIS THEORY
OF NATURAL SELECTION?
It can be broken down into four
basic tenets, or ideas
Theory of Natural Selection
• 1. Organisms are capable of producing huge
numbers of offspring.
• 2. Those offspring are variable in appearance
and function, and some of those variations are
heritable.
Theory of Natural Selection
• 3. Environmental resources are limited, and
those varied offspring must compete for their
share.
• 4. Survival and reproduction of the varied
offspring is not random. Those individuals
whose inherited characteristics make them
better able to compete for resources will live
longer and leave more offspring than those not
as able to compete for those limited
resources.
What is speciation and who
studies it?
• Speciation is the creation of a new
species
• Scientists who study the processes
and mechanisms that lead to such
speciation events are
EVOLUTIONARY BIOLOGISTS.
Allopatric Speciation
• A population becomes physically separated
from the rest of the species by a
geographical barrier that prevents
interbreeding.
• Because gene flow is disrupted by this
physical barrier, new species will form.
Sympatric Speciation
• Two populations are geographically
close to each other, but they are
reproductively isolated from each
other by different habitats, mating
seasons, etc.
Reproductive Barriers
A reproductive barrier is any factor that prevents
two species from producing fertile hybrids, thus
contributing to reproductive isolation.
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Habitat Isolation
Temporal Isolation
Behavioral Isolation
Mechanical Isolation
Gametic Isolation
Species
• A SPECIES is a group of similar
organisms that can mate to produce
fertile, viable offspring.
• Different species are, by definition,
REPRODUCTIVELY ISOLATED from
one another.
Adaptive Radiation
• Adaptive Radiation - Evolutionary
process in which the original species
gives rise to many new species, each
of which is adapted to a new habitat
and a new way of life.
E.g. Darwin's Finches
Evidence for Evolution
HOMOLOGY
• In biology, a HOMOLOGY is a
characteristic shared by two species
(or other taxa) that is similar
because of common ancestry.
Types of homology
• morphological homology – species placed in the
same taxonomic category show anatomical
similarities.
• ontogenetic homology - species placed in the
same taxonomic category show developmental
(embryological) similarities.
• molecular homology - species placed in the
same taxonomic category show similarities in
DNA and RNA.
MORPHOLOGICAL
HOMOLOGY
• Structures derived from a common ancestral
structure are called:
HOMOLOGOUS STRUCTURES
Ontogenetic Homology
The human embryo has gills, a tail,
webbing between the toes & fingers, &
spends its entire time floating and
developing in amniotic fluid has similar
salt concentration as ocean water
MORPHOLOGICAL
HOMOLOGY
• A structure that serves the same
function in two taxa, but is NOT
derived from a common ancestral
structure is said to be an
ANALOGOUS STRUCTURE
Examples of Analogous
structures:
• wings of bat, bird, and butterfly
• walking limbs of insects and vertebrates
• cranium of vertebrates and exoskeleton
head of insects
Molecular Homology
An ongoing process
• Evolution can be considered a process
of "remodeling" a population over the
course of many generations, with the
driving force being the natural
selection factors that favor one form
over another in specific environments.
Vestigial Structures
• Have marginal, if any use to the
organims in which they occur.
• EXAMPLES:
• pelvic elements in pythonid snakes and
cetaceans (whales)
• appendix in humans
• coccyx in great apes
Whale Pelvis?
Types of Evolution
• Divergent Evolution - Method of evolution
accounting for the presence of homologous
structures. Multiple species of organisms
descended from the same common ancestor at
some point in the past.
• Convergent Evolution - Method of evolution
accounting for the presence of analogous
structures. Organisms of different species often
live in similar environments, thus explaining the
presence of features with similar functions.
Rate of Evolution
• Gradual evolution occurs where the
increment of change is small compared to
that of time.
• Punctuated evolution occurs where the
increment of change is very large
compared to that of time in discrete
intervals, while most of the time there is
virtually no change at all.
Natural Selection in Action
Industrial Melanism
Natural Selection in Action
Camouflage
Natural Selection in Action
Mimicry
Coral vs. King Snakes:
Red on yellow, kill a fellow,
red on black won’t hurt Jack
Natural Selection in Action
Warning Coloration
Natural Selection in Action
Disruptive Coloration
Natural Selection in Action
Counter Shading
Natural Selection in Action:
Eye Spots
Causes of Evolution
1.
Mutations - random changes in genetic material at the
level of the DNA nucleotides or entire chromosomes
2.
Natural Selection - most important cause of evolution;
measured in terms of an organism's fitness, which is its
ability to produce surviving offspring
a. Stabilizing Selection - average phenotypes have a
selective advantage over the extreme phenotypes
b. Directional Selection - phenotype at one extreme has
a selective advantage over those at the other extreme
c. Disruptive Selection - both extreme phenotypes are
favored over the intermediate phenotypes
Natural selection favors the average individuals
within a population
Natural selection favors on one of the extreme
variations within a species
Individuals with both extreme phenotypes are selected for
Causes of Evolution
3. Mating Preferences - Organisms usually do not choose their
mates at random, thus the selection process can cause
evolution
4. Gene Flow - Transfer of genes between different
populations of organisms. This situation leads to increased
similarity between the two populations
5. Genetic Drift (Founder Effect & Bottleneck) - Situation
that results in changes to a population's gene pool caused by
random events, not natural selection. This situation can have
drastic effects on small populations of individuals. Common
on islands.
Gene Flow
Genetic Drift
The change in gene
frequency in a
population resulting in
different phenotypes
Founder Effect
Bottleneck Effect
The study of phylogeny
• Understanding a phylogeny is a lot like reading a family
tree.
• The root of the tree represents the ancestral lineage,
and the tips of the branches represent the descendents
of that ancestor.
• As you move from the root to the tips, you are moving
forward in time.
Phylogenic Speciation
• When a lineage splits (speciation), it is represented
as branching on a phylogeny.
• When a speciation event occurs, a single ancestral
lineage gives rise to two or more daughter lineages.
Shared Ancestry
• Phylogenies trace patterns of shared ancestry
between lineages.
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Each lineage has a part of its history that is
unique to it alone and parts that are shared with
other lineages.
Common Ancestors
• Each lineage has ancestors that are
unique to that lineage and ancestors
that are shared with other lineages —
called common ancestors.
Clades – Cladistics (The
study of clades)
• A clade is a grouping that includes a common
ancestor and all the descendents (living and extinct)
of that ancestor.
Nested Clades
• Clades are nested within one another — they form
a nested hierarchy.
• A clade may include many thousands of species or
just a few.
Reading Phylogeny
Evolution produces a pattern of relationships A B C D
among lineages that is tree-like, not ladder-like.
Reading Phylogeny
Just because we tend to read phylogenies from left to
right, there is no correlation with level of "advancement."
Reading Phylogeny
For any speciation event on a phylogeny, the choice of
which lineage goes to the right and which goes to the left
is arbitrary. The following phylogenies are equivalent:
Misconceptions about humans
It is important to remember that:
1. Humans did not evolve from chimpanzees. Humans
and chimpanzees are evolutionary cousins and
share a recent common ancestor that was neither
chimpanzee nor human.
2. Humans are not "higher" or "more evolved" than
other living lineages. Since our lineages split,
humans and chimpanzees have each evolved traits
unique to their own lineages.
Character Types
• A character is a recognizable feature of an organism. Characters
may be morphological, behavioral, physiological, or molecular.
• A shared character is one that two lineages have in common
• A derived character is one that evolved in the lineage leading up to
a clade and that sets members of that clade apart from other
individuals.
• Shared derived characters can be used to group organisms into
clades. For example, amphibians, turtles, lizards, snakes, crocodiles,
birds and mammals all have, or historically had, four limbs.
Review
So What Does This Mean?