3.1 Origin of Life (p. 62; Figs. 3.31, 3.32)
A. There are three possibilities for the origin of life on this planet: extraterrestrial origin, special creation, and evolution.
1. Only evolution can be tested scientifically.
B. Forming Life’s Building Blocks
1. The first organic molecules are believed to have formed spontaneously from building blocks subjected to lightning and UV radiation.
2. Miller and Urey reconstructed the oxygen-free early atmosphere, and conducted experiments that confirmed these beliefs.
3. Recent findings of even older fossils, however, have refuted their findings of their experiments.
4. Currently, a bubble model for the formation of early organic molecules is being examined.
3.2 How Cells Arose (p. 64; Figs. 3.33. 3.34, 3.35)
A. Scientists now suspect that the first macromolecules were not proteins but RNA molecules.
B. Not everyone accepts the notion that life evolved spontaneously on this planet, citing the second law of thermodynamics for evidence.
C. The First Cells
1. Most scientists believe that the first cells aggregated spontaneously as microdrops that eventually were able to incorporate molecules and energy.
2. It took millions of years for the first cell to develop.
D. Origin of Eukaryotic Cells
1. Endosymbiosis in the prokaryotes may have given rise to the eukaryotes.
E. Sexual Recombination
1. Sexual reproduction in eukaryotes allows genetic recombination and generates variation, leading to diversity.
F. Multicellularity
1. Diversity among eukaryotes was fostered by multicellularity and the specialization arising as a result.
G. The Kingdoms of Life
1. Living things fall into one of six kingdoms: Kingdom Archaebacteria, Kingdom Eubacteris, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, or Kingdom Animalia.
3.3 Origin of Life (p. 62; Figs. 3.31, 3.32)
C. There are three possibilities for the origin of life on this planet: extraterrestrial origin, special creation, and evolution.
2. Only evolution can be tested scientifically.
D. Forming Life’s Building Blocks
5. The first organic molecules are believed to have formed spontaneously from building blocks subjected to lightning and UV radiation.
6. Miller and Urey reconstructed the oxygen-free early atmosphere, and conducted experiments that confirmed these beliefs.
7. Recent findings of even older fossils, however, have refuted their findings of their experiments.
8. Currently, a bubble model for the formation of early organic molecules is being examined.
3.4 How Cells Arose (p. 64; Figs. 3.33. 3.34, 3.35)
H. Scientists now suspect that the first macromolecules were not proteins but RNA molecules.
I. Not everyone accepts the notion that life evolved spontaneously on this planet, citing the second law of thermodynamics for evidence.
J. The First Cells
3. Most scientists believe that the first cells aggregated spontaneously as microdrops that eventually were able to incorporate molecules and energy.
4. It took millions of years for the first cell to develop.
K. Origin of Eukaryotic Cells
2. Endosymbiosis in the prokaryotes may have given rise to the eukaryotes.
L. Sexual Recombination
2. Sexual reproduction in eukaryotes allows genetic recombination and generates variation, leading to diversity.
M. Multicellularity
2. Diversity among eukaryotes was fostered by multicellularity and the specialization arising as a result.
N. The Kingdoms of Life
2. Living things fall into one of six kingdoms: Kingdom Archaebacteria, Kingdom Eubacteris, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, or Kingdom Animalia.
Chapter 16 – Evolution of plants
16.1
Adapting to a Terrestrial Living (p. 354; Figs. 16.1, 16.2, 16.3,
16.4)
A. Plants are multicellular, terrestrial autotrophs that occur on land and derive energy through photosynthesis.
B. The green algae gave rise to the diverse land plants, which have now evolved into at least 266,000 different species.
C. Three major challenges had to be overcome for living on land: organisms had to absorb minerals, conserve water, and develop a new mode of reproduction suitable for land.
D. Absorbing Minerals
1. Many of the early plants had symbiotic fungi, such as the present-day mycorrhizae, to aid in the uptake of minerals and nutrients from rocky shores devoid of soil.
E. Conserving Water
1. A waxy cuticle evolved to help retard water loss.
2. Gases could be exchanged with the atmosphere through tiny openings called stomata that could also be closed to further reduce water loss.
F. Reproducing on Land
1. The development of spores was an evolutionary trend that protected reproductive cells from drying.
G. Transferring gametes from one plant to the next during sexual reproduction posed a problem that has been answered by the development of spores in many plant lines.
1. Haploid spores are produced by sporophytes, the diploid generation that alternates with the haploid gamete-producing gametophyte generation.
2. This alternation of generations solved many problems for plants reproducing sexually on land.
16.2
Evolution of a Vascular System (p. 356; Table 16.1)
A. As plants evolved greater specializations on land, below-ground root systems developed, along with vascular tissue to connect above- and below-ground portions of plants.
B. These “plumbing” systems are now specialized vascular systems that run from the very bottom of the roots to the tips of the shoots.
C. Plants that have evolved vascular systems are the most common types of plants found on earth at the present.
16.3
Nonvascular
Plants (p. 358; Figs. 16.5, 16.6)
A. Liverworts and Hornworts
1. Some plants that never evolved vascular systems can still be found.
2. The liverworts and hornworts are two groups of primitive plants that completely lack any kind of vascular system.
3. These small plants can only survive in moist habitats.
B. Plants with Simple Vascular Systems: Mosses
1. Mosses, a third type of fairly primitive plant, managed to evolve a simple, soft-sided tube capable of conducting water over short distances.
2. Strengthened tubes evolved later as vascular tissue in the true vascular plants.
3. In the liverworts, hornworts, and mosses, the main plant body is the gametophyte, with the sporophyte being borne on the gametophyte.
16.4
The
Evolution of Vascular Tissue (p. 359; Figs. 16.7, 16.8)
A.
Vascular plants have
specialized cells that can conduct materials and fluids.
B.
The remaining nine phyla of
plants have such vascular tissue, which enables them to grow to much greater
size than the nonvascular plants.
C.
The fossil record indicates
that vascular plants have been around for 430 million years and are different
from nonvascular plants in that they spend most of their time in the sporophyte
stage, have specialized conducting tissue, and have a specialized body form
made up of roots, stems, and leaves.
D. Two types of specialized conducting tissue can be found in vascular plants.
1. Phloem, made up of soft-walled sieve elements, conducts carbohydrates manufactured during photosynthesis from the leaves to the rest of the plant, and xylem, made up of hard-walled tracheary elements, conducts water from the roots upward to the rest of the plant.
E. How vascular plants grow has changed somewhat over the course of evolution.
1. Primitive vascular plants exhibited primary growth only, which involves elongation of roots and stems from a growing point called the apical meristem.
2. Vascular plants of today still exhibit this type of growth, but are also able to grow in width, called secondary growth, as a result of a cylinder of meristem lying beneath the bark.
3. Secondary growth produces wood.
16.5
Seedless
Vascular Plants (p. 360; Figs. 16.9, 16.10)
A. Four phyla of modern vascular plants lack seeds and rely on the presence of water to enable sperm to swim to their destination for fertilization.
B. Ferns are among the most abundant of the seedless vascular plants, and are especially numerous in the tropics.
C. The Life of a Fern
1. They exist as sporophytes with large leaves called fronds.
2. Spores are produced on the fronds and fall to the earth to develop into gametophytes.
3. On the small heart-shaped gametophytes, gametes are produced, fertilization occurs, and a new sporophyte grows.
16.6
Seed Plants
(p. 362; Figs. 16.11, 16.12, 16.13)
A. The evolution of seeds has greatly enhanced the ability of plants to survive on land.
B. A seed protects the developing embryo when it is most vulnerable to drying out or predation.
C. In seed plants, the gametophyte generation is even smaller than in seedless vascular plants, and gametophytes exist entirely within the sporophyte plant.
1. Microgametophytes, or pollen grains, are male gametophytes, and are transported by various means, depending upon the particular adaptations of a plant.
2. The female gametophyte is the megagametophyte, or ovule, which is fertilized only after pollination.
D. The first seed plants were the gymnosperms with incompletely enclosed ovules.
E. Angiosperms evolved later, with their ovules completely enclosed within a vessel called a carpel.
F. The Structure of a Seed
1.
A seed is made up of
the embryo of the sporophyte surrounded by a hard, protective seed coat.
2.
Nourishing endosperm
is also housed within the seed coat to provide a food source until germination.
3.
Seeds are adapted to
life on land because they enable better dispersal, or colonization of new areas
or better habitats, and because they protect the embryo during a period of
dormancy when the embryo is waiting for better conditions before germination.
4.
Seeds are also tuned
into the appropriate environmental cues that indicate when moisture and
temperature are optimal before germination and growth of the embryo out of the
seed.
16.7 Gymnosperms (p. 364; Figs.
16.14, 16.15)
A. Gymnosperms are represented on earth today by four different phyla: conifers, cycads, ginkgos, and the gnetophytes.
B. We are most familiar with the conifers whose needlelike leaves help resist water loss for these among the oldest and largest trees on earth.
C. The Life of a Gymnosperm
1. Conifers form two kinds of cones: seed cones that bear female gametophytes and pollen cones that produce male gametophytes.
2. Conifers rely on the wind to transfer pollen to the seed cone.
3. Once the sperm cell inside the pollen fuses with the egg cell, a new zygote is formed that can eventually develop into a sporophyte.
16.8
Rise of the
Angiosperms (p. 366; Fig. 16.16)
A. Angiosperms are probably the most successful land plants, comprising 235,000 species or 90% of all land plants.
B. Angiosperms evolved unique ways of transferring pollen for fertilization, which has ensured their survival, and special structures, called flowers, to attract and reward animal pollinators.
C. The Flower
·
Recognize which group
of algae gave rise to land plants and the nature of the problems this group had
to overcome to live on land.
·
List the adaptations
that evolved in groups of land plants to conserve water and to enable
reproduction on land.
·
Describe liverworts,
hornworts, and mosses.
·
Explain the nature of
vascular systems.
·
Discuss the advantages
and adaptations of seeds.
·
Compare gymnosperms
with angiosperms.
·
List the major groups
of gymnosperms.
2.1
A. English naturalist, Charles Darwin (1809-1882) was the first to propose natural selection as a mechanism of evolution in On the Origin of Species by Means of Natural Selection.
B. In
1. The views of
C. One
of the most influential events in
1.
During this voyage around the coasts of
2.2
A. The
fossils and patterns of life that
B. The
writings of geologist Charles Lyell (1797-1875) were highly influential to
1. Lyell believed, unlike most people of his day, that the earth was extremely old.
C.
What
1. Fossils of extinct armadillos were similar in form to living species.
2.
On the
3.
2.3
Inventing
the Theory of Natural Selection (p. 24; Figs. 2.7, 2.8, 2.9)
A. Darwin and Malthus
1. Mathematician Thomas Malthus (1798) wrote Essay on the Principle of Population in which he pointed out that human populations tend to increase geometrically while food supplies increase arithmetically.
2. However, populations remain fairly constant year after year because death limits population size.
3.
Malthus’s ideas provided the key that was needed for
B. Natural Selection
1.
2.
This led
3. The traits of organisms that survive to produce more offspring will be more common in future generations.
4.
C.
1.
D. Wallace Has the Same Idea
1. English naturalist Alfred Russell Wallace (1823-1913) wrote an essay about his own ideas on evolution by natural selection from his observations in Malasia.
2. Darwin and Wallace gave a joint presentation, then expanded his 1842 manuscript.
E. Publication
of
1.
2.
After 1860,
2.4 The Beaks of
A.
B. The Importance of the Beak
1. Beak shape of this group of 13 species of finches indicated a correspondence between shape and food source.
C. Was
1.
David Lack set out to test
D. A Closer Look
1. In 1973, the Grants of Princeton University discovered a relationship between beak shape, seed size, and climatic conditions which indicated that beak size was passed on from one generation to the next, and survival rate was adjusted to the food supply.
E.
1. Natural selection does seem to be operating to adjust the beak to its food supply.
2.5 Clusters of Species (p. 28; Fig.
2.13)
A.
B. Four groups of finches have been recognized from these islands: ground finches, tree finches, a warbler finch, and a vegetarian finch.
2.6 Hawaiian Drosophila (p. 29; Fig. 2.14)
A. The
adaptive radiation of 800 species of Drosophila
and Scaptomyza on the
2.7
A. Recent Radiation
1.
The
2. Dramatic changes in water level encouraged species formation.
B. Cichlid Diversity
1.
Cichlids are small, perchlike fish; over 300 species
were described in
2.
All
C. Abrupt Extinction
1.
In the 1950’s, the
2.
The
3.
The isolation of
4.
When the isolation broke down and the
2.8
A.
Periodic isolation appears to have played a role in
species formation in the alpine buttercups of
B.
The evolutionary mechanism responsible for inducing the
great diversity of alpine buttercups in
C. Fourteen species of buttercups occupy five distinct habitats.
D. Buttercup species have invaded these five habitats repeatedly as glaciers moved and isolated certain areas.
11 Evolution and Natural Selection
EXTENDED LECTURE OUTLINE
11.1 Gene Variation: the
Raw Material of Evolution (p. 252; Fig. 11.1)
A. Microevolution Leads to Macroevolution
1. Macroevolution is evolution on a grand scale, the formation of new species and major changes in family lineages.
2.
Microevolution, the kind
3. Adaptation results from microevolutionary changes that increase the likelihood of survival and reproduction.
B. The Key Is the Source of Variation
1.
2. New species evolve from existing ones because certain individuals have traits that allow them to produce more offspring that, in turn, carry the traits to the next generation.
3. Variation is not created by experience but already exists when selection acts on it.
11.2 The Pace of Evolution
(p. 253; Fig. 11.2)
A. Different types of organisms evolve at different rates.
1. Mammals evolve slowly, and certain groups of fish evolve even more slowly.
B. Evolution in Spurts?
1.
Two opposing viewpoints about
how rapidly speciation occurs are now being hotly debated.
2.
A hypothesis of gradual
evolutionary change, called gradualism, assumes that macroevolution occurs at a
constant, gradual pace.
3.
The contrasting model,
punctuated equilibrium, predicts that major environmental changes trigger
bursts of rapid speciation, followed by periods of gradual change.
4.
The fossil record supports
both of these hypotheses.
5.
In some lineages, speciation
has been progressive and gradual.
6. In others, many new species appear all at once.
11.3
The Fossil
Record (p. 254; Figs. 11.3, 11.4, 11.5)
A. The most direct evidence of macroevolution is found in the fossil record.
B. Fossils are the preserved remains, traces, or tracks of once-living creatures.
C. Dating Fossils
1.
In
2. Today, rocks are dated by measuring the rate of decay of certain radioisotopes contained in the rock.
D. A History of Evolutionary Change
1. When fossils are lined up according to their age, they often provide evidence of successive evolutionary change.
2. Many examples serve to illustrate a record of successive change and are one of the strongest lines of evidence of evolution.
E. Gaps in the Fossil Record
1. Today the fossil record is very complete and few gaps exist.
2. Among the vertebrates, fossils have been found linking all the major groups.
11.4
The
Molecular Record (p. 256; Figs. 11.6, 11.7, 11.8, 11.9)
A. The evolutionary past is also evident at the molecular level.
B. Since the record of evolutionary change is linked to changes in DNA, organisms that are more distantly related will have accumulated a greater number of genetic changes in DNA.
C. Molecular Clocks
1. When analyzing nucleotide sequences for the gene encoding the protein cytochrome c, biologists can construct a molecular clock showing the relatedness of organisms based on how many nucleotide sequences they are away from each other.
D. Proteins Evolve at Different Rates
1. Not all proteins evolve at the same rate.
2. Cytochrome c and hemoglobin have changed at relatively constant rates, but other proteins, like the fibrinopeptides, evolve considerably faster.
E. Phylogenetic Trees
1. Phylogenetic (family) trees can be constructed showing the relatedness of organisms based on both fossil and molecular evidence.
11.5
The
Anatomical Record (p. 258; Figs. 11.10, 11.11, 11.12)
A. Development
1. Many diverse organisms go through the same early stages of embryologic development, which is evidence for evolutionary relatedness.
B. Sharing the Same Parts
1. In vertebrates, homologous structures can be seen from the study of anatomy.
2. Vertebrate forelimbs have diverged to perform different functions, but consist of the same bone structure, indicating a common ancestry.
3. Sometimes analogous structures are found in animals that have evolved the same solution to a problem, although they did not share a common ancestor.
C. “Leftover” (Vestigial) Organs
1. Vestigial organs—which served a function in an ancestor but have no function in the modern counterpart (such as the appendix that has no function in humans but functions as a reservoir for cellulose bacteria in apes)—are also anatomical evidence for evolution.
11.6
The
Hardy-Weinberg Principle (p. 260; Figs. 11.13, 11.14)
A. Population genetics is the study of the properties of genes in populations.
B. Genes Within Populations
1.
The proportion of alternative
forms of a gene, or alleles, in a population can be calculated and the allele
frequencies determined.
2.
The equations of
Hardy-Weinberg equilibrium can then be used to predict the frequencies of
genotypes in future populations.
3.
According to Hardy and
Weinberg, gene frequencies do not change when the size of the population is
large, when mating occurs at random, when natural selection is not occurring,
and while there are no mutations or migration.
4.
The symbol p denotes the frequency of the dominant
allele, and q stands for the
frequency of the recessive allele.
5.
By definition, p + q
= 1.
6. By expanding the binomial, (p + q)2 = p2 + 2pq + q2 = 1, where p2 is the proportion of homozygous dominant individuals in the population, 2pq indicates the proportion of heterozygotes, and q2 is the proportion of homozygous recessives.
11.7
Why Do
Allele Frequencies Change? (p. 262; Fig. 11.15; Table 11.1)
A. Five factors alter the proportions of homozygotes and heterozygotes enough to produce significant deviations from the proportions predicted by the Hardy-Weinberg principle.
B. Mutation
1. Genetic mutations, or alterations in DNA nucleotide sequences, add new combinations to the genetic makeup of a population.
C. Migration
1. Migration from the movement of individuals into or out of the population can be a source of new genetic variation.
D. Genetic Drift
1. In small populations, by random chance alone, it is possible for the allele frequencies to change from one generation to the next.
2. Such a phenomenon is termed genetic drift.
3. As local subgroups are isolated from the main population, genetic drift occurs in them as well. The founder effect occurs when a few individuals are separated from the rest and give rise, over time, to a new population; this effect often occurs on islands.
4. The founder effect is somewhat similar to the bottleneck effect in which a few members of a population of species are all that are left to give rise to the next generations of that species.
5. The bottleneck effect limits the genetic diversity of a population and can lead to the appearance of recessive mutations.
E. Nonrandom Mating
1. Nonrandom mating and inbreeding (mating with relatives) also lead to changes in gene frequencies from one generation to the next.
F. Selection
1. Selection, whether artificial selection by humans or natural selection, operates to select certain fit phenotypes, which add more genes to successive generations.
11.8
Forms of
Selection (p. 264; Figs. 11.16, 11.17, 11.18)
A. How selection changes the population depends on which genotypes are favored.
B. Three types of selection have been observed in natural populations.
C. Disruptive Selection
1. In disruptive selection, both extremes are favored to the demise of the middle phenotype.
2. Disruptive selection is much less common than the other two types of selection.
D. Stabilizing Selection
1. In stabilizing selection, individuals toward the middle of the range are selected.
E. Directional Selection
1. Directional selection favors a phenotype at one extreme or the other of the population.
11.9
Sickle-Cell
Anemia (p. 266; Figs. 11.19, 11.20, 11.21)
A. Sickle-cell anemia is a hereditary disease in which the homozygous condition is often lethal.
B. The Puzzle: Why So Common?
1.
In central
C. The Answer: Stabilizing Selection
1. Sickle-cell anemia in humans is an example of stabilizing selection in which the middle phenotype, in this case the heterozygote with sickle-cell trait but not anemia, is more adapted to an environment that hosts the malarial parasite.
2. Heterozygotes are resistant to the malarial parasite that otherwise kills the person with normal hemoglobin; those with sickle-cell anemia perish due to this genetic abnormality.
11.10
Peppered
Moths and Industrial Melanism (p. 268; Figs. 11.22, 11.23)
A. Historically,
the peppered moth in
B. Selection for Melanism
1. When trees were in their normal condition, with light-colored bark, the light morph of the peppered moth could easily hide from its predators.
2. When the trees were darkened with soot, the dark morphs of the peppered moth were at an advantage.
C. Industrial Melanism
1.
The adaptations of the
dark moth in populations of Biston
betularia during a period that triggered this industrial melanism in
D. Selection Against Melanism
1. Once pollution was controlled and the soot disappeared from trees, the light-colored moth was again favored and became abundant in the population.
E. Reconsidering the Target of Natural Selection
1. One hypothesis of peppered moth abundance tried to correlate the presence of lichens on the trees to the presence of moths with no clear conclusion.
11.11
The Species
Concept (p. 270; Fig. 11.24)
A. According to
B. A species is defined as a group of organisms that is unlike other such groups and that does not integrate extensively with other groups in nature.
C. Species formation is the final step of a long process in nature.
1. Two separate local populations become adapted to the unique aspects of their own environments and, after a period of time, they are considered different enough to be called ecological races.
2. Natural selection reinforces the differences; these changes are isolating mechanisms.
11.12
Prezygotic
Isolating Mechanisms (p. 271; Fig. 11.25)
A. Isolating mechanisms, whether physical or behavioral, prevent interbreeding, and can lead to reproductive isolation after which separate species might exist.
B. Prezygotic isolating mechanisms lead to reproductive isolation by preventing the formation of hybrid zygotes.
11.13
Postzygotic
Isolating Mechanisms (p. 272; Table 11.2)
D. Postzygotic isolating mechanisms include improper development of hybrids and failure of the hybrids to become established in either parental habitat.
·
Explain how
microevolutionary changes can accumulate, leading to macroevolution.
·
Discuss how natural
selection on variants within populations leads to the evolution of different
species.
·
Describe evidence for
evolution as supported by the fossil record.
·
Describe how molecular
evidence for evolution supports the fossil record.
·
List the types of
evidence for evolution shown by comparative anatomy.
·
Know how to use the
Hardy-Weinberg equilibrium equation.
·
Understand how gene
frequencies change from one generation to the next due to mutation, migration,
genetic drift, nonrandom mating, and selection.
·
Give examples of the
three types of selection.
·
Discuss the case of
sickle-cell anemia as an example of evolutionary adaptation.
·
Explain how natural
selection favors different morphs of peppered moths in different situations.
·
Differentiate between
how prezygotic and postzygotic isolating mechanisms lead to reproductive
isolation.