Download Classification and Adaptation

Biological Evolution
Diversity and Relationships
• Charles Darwin (1809-1882) was an English scientist
who began as a naturalist aboard a ship that sailed all
over the world.
• Darwin became curious about the diverse creatures that
he saw and the possible relationships between them.
• He searched for a reason why
organisms change over time
• He observed that there were many
struggles for survival: finding mates,
food, and shelter while escaping
predators and sickness
• From this he identified the process
of natural selection
Natural Selection
• For years, people had bred specific organisms
to have certain traits – artificial selection
– Ex. breeding corn plants that produce the most ears
• Natural Selection occurs when organisms with certain
traits survive, reproduce, and pass on those traits to
the next generation.
– Ex: A faster fish may be better suited for escaping predators
and live to produce offspring with that same variation
– A slower fish may be more easily caught by a predator and
never live to reproduce and pass on that trait
• This is often described as “Survival of the Fittest”
Four Principles of Natural Selection
1. Overproduction of offspring – having many offspring
raises the chance that some will survive
2. Variation – Variation exists in the inherited phenotypes
of the individuals within every population. An organism’s
phenotype may influence its ability to find, obtain, or
utilize its resources (food, water, shelter, and oxygen) and
also might affect the organism’s ability to reproduce.
Phenotypic variation is
controlled by the
organism’s genotype
and the environment.
Four Principles of Natural Selection
3. Adaptation - The process of adaptation leads to the increase in
frequency of a particular structure, physiological process, or
behavior in a population of organisms that makes the organisms
better able to survive and reproduce.
– “Fitness” is used to measure how a particular trait contributes to the
reproductive success in a given environment and results from adaptation
4. Descent with modification - As the environment
of a population changes, the entire process of
natural selection can yield populations with new
phenotypes adapted to new conditions. Natural
selection can produce populations that have
different structures, live in different niches or habitats from
their ancestors. Each successive living species will have
descended, with adaptations or other modifications, from
previous generations.
Examples of Adaptations
Genetic Processes
Most scientist attribute the continuity of lifeforms over time to the genetic processes that
all organisms share:
1. All life that has ever existed on Earth share at
least the same two structures:
– Nucleic Acids (DNA or RNA) that carry the
code for the synthesis of the organism’s proteins
– Proteins which are composed of the same twenty
amino acids in all life forms
2. The same sequences of nucleotides code for
the same specific amino acids.
Reproduction
Sexual
• Genetic Varity Due to:
– Gene shuffling, crossingover, recombination of
DNA, mutations
• Genetic changes result in
changes in the phenotype
• Different allele
combinations produce traits
that can improve individuals
chances of survival
Asexual
• Genetic Varity: can only
occur through mutations in
DNA passed from parent to
offspring
• Examples:
– Binary fission, budding,
fragmentation, vegetative
propagation
• Offspring are generally
genetically identical to
their parent
Diversity within a Species
• All the genes, including different alleles, in a given
population is called the “gene pool”
– Diversity within a species makes it more likely that the right
adaptation could be present – therefore, an increase in
diversity increases its chances of survival
5 Factors That Can Affect Genetic Variability
1. Genetic Drift - the random change in the frequency
of alleles of a population over time. Due to chance,
rare alleles in a population will decrease in frequency
and become eliminated; other alleles will
increase in frequency and become fixed
2. Gene Flow - the movement of genes
into or out of a population. This occurs
during the movement of individuals between
populations (such as migration) thus increasing the
genetic variability of the receiving population.
5 Factors That Can Affect Genetic Variability
3. Non-random Mating – Mating among individuals
with favorable traits (such as coloration or odors in
plants and animals, competitive strength, courting
behaviors) results in the gene pool of a population
that can change over time and a species that can
become increasingly adapted to its environment.
4. Mutations - increase the frequencies and
types of allele changes within the
population
5. Natural Selection - allows for the most
favorable phenotypes to survive and thus
be passed on to future generations.
Hardy-Weinberg Principle
• When there is no change in the allele frequencies in a
species, the population is in genetic equilibrium.
• This concept is known as the Hardy-Weinberg
Principle. To sustain equilibrium, the must be:
–
–
–
–
–
A very large population with no genetic drift
No movement into or out of the population
Random mating
No mutations with the gene pool
No natural selection
Godfrey Hardy
(1877-1947)
Wilhelm Weinberg
(1862-1937)
Evidence of Biological Evolution
• The changes in inherited traits in a species over time is called
biological evolution.
– Microevolution occurs on a small scale affecting a single population
– Macroevolution occurs on a large scale affecting changes in species
across populations
• We can look at common adaptations to trace the history of different
organisms and see how they may have evolved from a common
ancestor.
• The species we see today evolved from species of former periods in
time
• Other Evidence
of
Evolution
– Paleontology
– Anatomy
– Embryology
– Biochemistry
Paleontology
• Paleontology is the study of prehistoric life
• Fossils are preserved remains of organisms that lived many
years ago
• Comparing current and ancient species shows a pattern of
gradual change from the past to the present.
• Examining the fossil record of Earth reveals the history of
organisms that have lived on Earth (including those that are
extinct) and the relative ages of those fossils.
• The fossil record is not complete because most organisms do
not form fossils. Many of the gaps in the fossil record have been
filled in as more fossils have been discovered.
• The older the fossils, the less resemblance there is to modern
species.
Anatomy
• Anatomy is the study of the structures of organisms
• Structures in different species
with common evolutionary
origin are called
homologous structures
• The can be similar in:
– Arrangement
– Function
– Both
• Scientists view homologous structures as evidence of a common
ancestor because it would be unlikely for so many animals to
have similar structures if they developed individually.
• The study of evolutionary relationships between homologous
structures is called Comparative Anatomy
Anatomy
• Similar function of a body
feature does not always mean
they have a common ancestor.
• The wings of birds and insects
evolved from distinctly
different groups of ancestors.
• Though their wings are alike in
function, they differ in
structure.
• Body parts of organisms that
do not have similar ancestry
are called analogous
structures.
Anatomy
• Vestigial Structures also provide evidence of
common ancestry.
• Vestigial Structures have little or no function in
an organism but were probably useful to an
ancestor.
• Example:
– Our tailbone (coccyx) – has no current
function but may once have
been helpful to our ancestors
– The eyes of blind mole rats
– Pelvis of a snake
– The muscles in human ears
Embryology
• Embryology is the study of embryo development in organisms
– The could include pre-birth, pre-hatching, or pre-germination
• The study of this development in different species is called
comparative embryology
• Studying the structures of embryos can lead to clues of possible
ancestors
• The embryos of fish, reptiles, birds, and mammals all have a tail
and gill slits even though they may not exist on the mature
organism
Biochemistry
• Biochemistry is the study of chemical processes in
organisms
• The study of the ability of different species to
synthesize substances is called comparative
biochemistry.
• Comparison of the DNA sequences of two species
provides some of the most reliable evidence.
• Organisms with the common ability to synthesize a
specific substance may be evidence of a common
ancestor.
– All citrus trees can produce citric acid
and therefore may have developed
from a common ancestor
Patterns of Biological Evolution
• Speciation is the process of forming a new species by
biological evolution from a preexisting species
1. Gradualism - Gradual changes of a species in over long
periods of time
– Ex - gradual trend toward larger or smaller body size.
2. Punctuated Equilibrium - Periods of abrupt
changes in a species after long periods of little
change within the species over time
– Ex - sudden change in species size or shape due to
environmental factors
Patterns of Biological Evolution
3. Divergent Evolution - a number of different
species diverge (split-off) from a common
ancestor. This occurs when, over many
generations, organisms (whose ancestors were
all of the same species) evolve a variety of
characteristics which allow them to survive in
different niches.
Patterns of Biological Evolution
4. Convergent Evolution - Evolution among different
groups of organisms living in similar environments
produce species that are similar in appearance and
behavior. Convergent evolution has produced many of
the analogous structures in organisms today.
Patterns of Biological Evolution
5. Coevolution - when two or more species living
in close proximity change in response to each
other. The evolution of one species may affect
the evolution of the other.
Patterns of Biological Evolution
6. Extinction - the elimination of a species often occurring
when a species cannot adapt to a change in its environment.
This can be gradual or rapid.
– Gradual extinction - occurs at a slow rate and may be due to other
organisms, changes in climate, or natural disasters.
– Mass extinction - occurs when a catastrophic event changes the
environment very suddenly (such as a massive volcanic eruption, or a
meteor hitting the earth causing massive climatic changes). It is often
impossible for a species to adapt to rapid and extreme environmental
changes.
• A Phylogenetic Tree shows the
relationship of different
organisms believed to have a
common ancestor based on
taxa (groups)
• Branches from an intersection
show those with a common
ancestor
• You can see that the snail,
earthworm and insect have a
more recent common ancestor
than the snail and sea star
Time
Evolutionary Relationships
Classification of Life
• All living things can be classified as belonging to one of
3 Domains
– Bacteria
- Archaea
- Eukarya
• All living things can be classified as belonging to one of
the 6 Kingdoms of Life
–
–
–
–
–
–
Archaeabacteria
Eubacteria
Protista
Plantae
Fungi
Animalia
Kingdom Characteristics
Dichotomous Key
A dichotomous key is a tool that allows the user to determine the identity of
items in the natural world, such as trees, animals, or rocks. Keys consist of a
series of choices that lead the user to the correct name of a given item.
"Dichotomous" means "divided into two parts". Therefore, dichotomous keys
always give two choices in each step.
1. a. wings covered by an exoskeleton ………go to step 2
b. wings not covered by an exoskeleton ……….go to step 3
2. a. body has a round shape ……….ladybug
b. body has an elongated shape ……….grasshopper
3. a. wings point out from the side of the body ……….dragonfly
b. wings point to the posterior of the body ……….housefly