vizualizing earth history by loren e. babcock chapter 5 biological evolution

VIZUALIZING EARTH HISTORYBy Loren E. Babcock

Chapter 5

Biological Evolution

Evidence of Biological Evolution and Natural Selection

Explain the meaning of biological evolution.Evolution - Change through time (usually applied to

biological organisms).

Changes that occur within a species or population from one generation to the next, as parents pass their morphologic, behavioral, and other traits on to their offspring, represent microevolution.


Darwinian synthesis

By the mid 1800s, biological evolution had become widely accepted as a scientific theory. Although it was (and still is) accepted by practicing scientists

with the highest degree of certainty, opinion differed on its driving force.

The mechanism that drives biological evolution —natural selection—

was first put forward in separate publications by Charles Darwin and Alfred Russell Wallace (1859).


Explain natural selection and how it operates.

Natural selection - The process by which individuals best suited to their environment survive and

reproduce, and less well suited individuals are eliminated from the population.

To provide supporting evidence for the concept of natural selection, Darwin addressed embryology,

homologous structures, vestigial structures, breeding

experiments, the fossil record, and adaptation.



Homologous structures - Morphological features in biological organisms that have a similar position and evolutionary origin, but not necessarily identical structure or the

same function.

Analogous structures - in organisms have essentially the

same function, but different evolutionary origins. Birds,

bats, and insects have all evolved wings for flight, but

they have done so by different evolutionary means.



Vestigial structure - Structure in an organism, usually

reduced in size or function compared to the homologue

in earlier species of the evolutionary lineage; it is

in the process of disappearing.

Selective breeding – is a process in which humans decide which desirable traits should be concentrated in breeding, is exemplified in the many breeds of dogs, all of which have a single ancestor, the gray

wolf.



Adaptation - The process of modification of an organism or its parts making it more fit for

survival in an ecological niche. The word can also refer to a

trait that helps an organism survive in its ecological

niche.

Darwin and Wallace separately proposed natural selection as the mechanism to explain how descent

with modification (or evolution) happened.

Natural selection is based on the observation that populations (or species) are usually composed of more individuals than the environment can

support.

Variation and Inheritance of TraitsExplain the origin of variation in populations and

explain how changes can be inherited.

Gregor Johann Mendel carried out experiments on garden peas in the 1850s and 1860s,

demonstrated distinct, replicable patterns underlying

inheritance, and developed a conceptual model for heritability that explained the patterns.

The work laid the foundation for modern genetics, which is the branch of biology concerned with

heredity and variation.

Punnett Square

Variation and Inheritance of TraitsUnderstand the structure of genetic material.

Genetics - The branch of biology concerned with heredity

and variation.

Genetic changes underlie the morphological changes recorded in the fossil record. Genetic variation and inheritance of adaptive traits

make natural selection possible.

Genetic changes in modern organisms can be used to track evolutionary history, and even

to provide some sense of the timing of evolutionary events.

Variation and Inheritance of TraitsUnderstand the structure of genetic material.

Variation and Inheritance of TraitsModern genetics: genes, chromosomes, DNA

Gene - Unit of chromosomal information about a heritable trait that is passed on from parents

to offspring.

Chromosome - Genetic structure by which hereditary information is physically transmitted from one

generation to the next.

The DNA molecule usually consists of two spiral strands, known

as a double helix. It contains genes, which are the hereditary

units that Mendel thought of as unit factors.


Cells store genetic information in DNA (deoxyribonucleic acid) molecules.

In eukaryotes, the DNA resides in the cell nucleus, but prokaryotes lack a

nucleus to contain the DNA.


Meiosis - Division of chromosomes to produce two haploid cells as gametes necessary for sexual reproduction

are produced.

Mitosis - Division of cell nuclei in which the parental chromosomal number is

maintained; it is the basis for bodily growth and asexual reproduction.

Variation and Inheritance of TraitsMutations, adaptations, and random factors

Mutation - Heritable change in DNA or chromosomal structure that results in new versions of genes,

and ultimately, of life’s diversity.

Molecular clock - The concept that genetic mutations occur at a known rate, and if the rate is known, the

number of genetic differences between separate species can be used to measure the amount of

time that has elapsed since the species diverged.

Variation and Inheritance of TraitsMutations, adaptations, and random factors

Speciation processes

Speciation - The evolution of a new species from an ancestral species.

Speciation, or the rise of a new species from an ancestral species,

in sexually reproducing organisms, can occur according to one of three general models.

Allopatric Speciation

Sympatric Speciation

Parapatric Speciation

Speciation: Processes and Rates

Allopatric speciation, emphasizes disruption of gene flow between populations, usually by some sort of

physical barrier.

Sympatric speciation, involves the rise of a daughter

species from a group of individuals within the geographic

range of an ancestral species.

Parapatric speciation, a daughter species might arise

through hybridization of two populations.

Speciation: Processes and RatesSpePECIATION PROCESSES

The fossil record shows two different speciation patterns,

cladogenesis and anagenesis.

Cladogenesis is a branching speciation pattern, and it applies

to populations that become reproductively isolated and then

diverge genetically from each other.

Anagenesis refers to changes in allele frequencies that occur

along a single evolutionary pathway. The parent species

and daughter species are connected by intermediates.

Speciation: Processes and RatesSPECIATION RATES

Charles Darwin’s claimed that evolution occurred slowly, the result of a gradual accumulation of changes from one generation to the next and through phylogeny, or an evolutionary series.

Phylogeny - The line or lines of descent in an evolutionary series.

Phyletic gradualism - Speciation rate characterized by

a slow, gradual pace.


Niles Eldredge and Stephen Jay Gould proposed punctuated equilibrium as a theory of evolutionary

biology.

Punctuated equilibrium - sexually reproducing populations

experience little change for most of their geological history,

and that when phenotypic evolution does occur, it is localized

in rare, rapid events of branching speciation (called cladogenesis).

Phyletic gradualism – Contrasts with punctuated equilibrium,

because it states that evolution generally occurs uniformly

and by the steady and gradual transformation of whole

lineages (anagenesis).

Phylogenetics: Reconstructing Evolutionary HistoryUnderstand how an evolutionary hypothesis is

represented on a cladogram.

A group of species that includes the ancestor and all of its

descendants is called a clade (monophyletic group or natural

group). The classification of species will follow along the lines

of clades, but in practice this is not always the case. Instead,

so-called artificial taxa are used in many circumstances. There

are two basic types of artificial taxa:

1, paraphyletic groups, in which one or more groups descended

from the common ancestor are excluded from the group; and

2, polyphyletic groups, in which members of the group

have separate ancestors.

Evolutionary Patterns and Trends

Study of evolutionary history shows that certain patterns or

trends have occurred in group after group over a period

of millions of years.

IRREVERSIBILITY OF EVOLUTIONEarly in the 20th century, the Belgian

paleontologist Louis Dollo observed that evolution cannot produce

exactly the same species more than once. This concept of the irreversibility of evolution

has come to be known as Dollo’s Law.

Evolutionary Patterns and TrendsCONVERGENT EVOLUTION

Convergent evolution is the evolution of similar body forms in

two or more biological groups. Similar body forms apparently

evolved in different taxa that used similar ecological

strategies, or as a response to similar ecological pressures.

Adaptive radiation - Rapid evolution of organisms to fill

new ecological niches. Adaptive radiation occurs when

life forms rapidly diverge to fill a variety of niche spaces

that have become open to them.


Charles Darwin’s claimed that evolution occurred

slowly, the result of a gradual accumulation of changes from one generation to the next and through phylogeny, or an evolutionary series.

Phylogeny - The line or lines of descent in an evolutionary series.

Phyletic gradualism - Speciation rate characterized by

a slow, gradual pace.

Evolutionary Patterns and TrendsAdaptive radiations – Increase in body size

In the late 1800s, the American paleontologist Edward Drinker Cope observed a common tendency for animals to increase in body size through an

evolutionary lineage. This trend is often called Cope’s Rule.

Horses, for example, were represented in the Eocene by a small

animal known as Hyracotherium. Subsequent horses tended

toward larger size. The living species, Equus caballus, is about

four times the size of Hyracotherium.

Evolutionary Patterns and TrendsAdaptive radiations - Heterochrony

Heterochrony involves evolutionary changes in a lineage

that result from changes in developmental timing. There are two forms of heterochrony:

Paedomorphosis, adults of the descendant species look much like juveniles of the ancestor.

Peramorphosis, the onset of sexual maturity in the descendant

is delayed in comparison to the ancestor. The descendant

continues to show development of characters that the ancestor did not show.

Evolutionary Patterns and TrendsAdaptive radiations - Asymmetry

Natural selection has had a long history of reinforcing

right-left behavioral differences in species.

Ambidextry, or equal capability of the right and left sides, has tended to be selected against.

It seems more adaptive for individuals to have a preferred lead side if they are to perform well in most functions, especially

running or swimming from predators.

Extinction

Extinction is the annihilation of all individuals of a species.

Every species that evolves eventually becomes extinct,

so extinction can be view as a natural part of the

evolutionary process. A certain percentage of the

world’s species can be expected to become extinct

during any interval of geologic time, and the normal

flux of extinction can be thought of as the background

level of extinction.

Mass extinction - When numerous species become extinct within a geologically short time

interval.

vizualizing earth history by loren e. babcock chapter 5 biological evolution

Documents

biological organisms

evolution change

natural selectionexplain

supporting evidence

vestigial structures

process of modification

analogous structures

process of disappearing