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Principles of Biology - Biology 111
Fall Quarter
Lake Tahoe Community College
Instructor: Ralph Sinibaldi
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Ch. 14 – Evolution of Biological Diversity
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I. Asteroids
A. 65 mya, dinosaurs and half of all other species went extinct. Why?
B. 1981, 2 petroleum geologists found large crater off Yucatan peninsula in Mexico (Fig. 14.1)
C. Macroevolution is the multiplication of species (Fig. 14.2)
1. nonbranching
2. branching
II. Concept of species _ Mayr in 1927, New Guinea – ID 138 birds; local natives named 137
A. What is a species? (Fig 14.4)
1. biological species
a. descent from a common ancestral population
b. reproductive compatibility – biological species definition – limits
1. asexually reproducing species
2. fossils
3. some different species can mate – horses and donkeys
c. no abrupt differences btn populations in genotype and phenotype
2. Taxonomy is branch of biology concerned with naming and classifying the diverse forms of life
3. Carolus Linneaus – Swedish botanist developed binomial nomenclature in 18th century
B. Reproductive barriers keep species separate.
1. repro barriers keep similar species w/overlapping ranges from interbreeding (Fig. 14.5)
how do populations diverge so that there are reproductive barriers between but not within
populations? takes long periods, maybe 10k to 100k years.
2. Prezygotic barriers
a. temporal isolation – reproduction occurs during different times, e.g. seasons
b. habitat isolation - different places in same area e.g. above ground mosquitoes and
below ground mosquitoes
c. behavioral isolation – mating or courtship signals differ e.g. birds w/ different songs
(Fig. 14.6)
d. mechanical isolation – reproductive parts of male fit only females of same species for
many insects; hummingbird bill fits only particular flower it pollinates
e. gametic isolation – sex can happen, but sperm and egg do not unite e.g. sea urchins
release eggs and sperm in water, but only unite if same molecules on surface of
gametes
3. Postzygotic barriers
a. hybrid inviability – hybrids extremely frail, do not complete development or life cycle
eg. Species of frogs genus rana
b. hybrid sterility – offspring are sterile eg. Mules (Fig. 14.7)
c. hybrid breakdown – 1st gen. Hybrids are viable and sterile, but when they mate, their
offspring are not viable or are sterile
II. Mechanisms of Speciation
A. allopatric speciation (Fig 14.8) - geographic separation causes speciation
1. how large a barrier depends on species – birds need larger barrier than salamanders
a. adaptive radiation -emergence of numerous species from a common ancestor
introduced to new and diverse environments e.g. Darwins finches– all 14 species on
finches on Galapagos evolved from one small ancestral group
B. sympatric speciation - same home range, speciation occurs 1. polyploidy in plants (Fig. 14.11)
2. Vernal Pools in California, desert pupfish - drying trend in formerly wet death valley produced
desert pools with different spp of pupfish
C. Tempo of speciation can be steady or jumpy (fig. 14.14)
1. Gradualist model – fits Darwin’s model – many small accumulations over BIG time result in
BIG changes (speciation)
2. Punctuated equilibrium – Non gradual changes in fossil record –
a. avg. successful species survives for a few million years
a. mutation can cause rapid changes, then the species remains unchanged in fossil record
for millions of years.
III. Evolution of Biological Novelty
A. Key adaptations may enable species t survive and proliferate after mass extinctions.
1. What enables some organisms to live and proliferate after cataclysmic events, and causes others to
die out?
a. chance
b. key adaptations (feathers on birds, mammary glands and fur in mammals) (Fig. 14.15)
c. exaptation – structure evolved for one purpose may evolve to have another purpose; feathers
probably first evolved for insulation, not flight; flight probably began as large hops
d. bromeliads – some thrive in arid soils, most are epiphytes; pineapples – base of leaves is
water catchment; epiphytic bromeliads also use water catchment strategys.
B. Evo – devo - Evolutionary and Developmental biology – genes that control development
1. Changes in timing of developmental processes may have huge effects on the ensuing organism. (Fig.
14.16)
2. Retention of juvenile features in adult forms e.g. humans have a long childhood not shared by
primates. (childhood = extended period btn. infancy and adulthood. ex. big heads, big eyes, short
legs- we feel affectionate toward the young - see Mickey Mouse over time (Fig.14.17).
IV. Earth History and Macroevolution
A. Fossil Record chronicles macroevolution –major changes in the history of life on earth – includes speciation
and increase in biodiversity through speciation, and also encompasses origin of evolutionary novelties, like
feathers on birds (Fig. 14.18)
1. Geologic time scale (Table 14.1) – provides overview of macroevolution
Precambrian - microbes began about 3.5 billion ya, invertebrates about 600 mya.
Paleozoic - 570 mya - origin of most modern animal phyla
Mesozoic - rise of gymnosperms and flowering plants
Cenozoic - proliferation of mammals, birds, insects, and humans only about 100,000 ya
B. Radiometric dating - Carbon 14 - radioactive with a fixed rate of decay – (Fig. 14.19)
1. Carbon 12 is normal. C14, less common, has a half life of 5700 years.
2. Radiocarbon dating can be done using proportions of C12 to C14, as well as the half life of the
isotope.
3. To date fossils older than 50,000 yr old, paleontologists use other isotopes with longer half lifes. For
example, Potassium 40 is an isotope with a half life of 1.3 billion years. It can be used to date rocks
and other fossils hundreds of millions of years old.
4. Error factor of radiometric dating is about 10%
C. Continental drift has played a major role in macroevolution
1. Alfred Wegener proposed idea of continental drift in 1912.
2. continental drift - plates on the earth’s surface that move around due to the degassing of the earth’s
molten interior. Europe and N. America are drifting apart at rate of 2 cm/yr. Over time, this is huge.
3. (Fig. 14.20) Pangaea - as supercontinent formed and broke apart, many species went extinct due to
climate changes (drier and more varied), paving way for proliferation in species of survivors
a. marsupials probably evolved in N. America, spread to Australia while continents still joined.
b. Lungfishes found in 3 continents; suggests they evolved on Pangaea
D. Mass extinctions result in diversification and proliferation of remaining life forms
1. 65 mya, at end of Cretaceous, mass extinction occurred, ending the age of dinosaurs.
2. 6 mass extinctions in the last 600,000,000 years. Losses escalated to 6x the average rate of
extinction.
3. The survivors may have more environmental options in these cases. Mammals existed for at least 75
million years before undergoing explosive increase in diversity just after the Cretaceous. If dinosaurs
had not be largely wiped out, the flora and fauna of earth today might be entirely different.
II. Classifying the Diversity of Life
A. Reconstructing phylogeny is part of systematics, science of biological classification.
B . Fig. 14.22- Taxonomy = identification and classification of species. Scientific nomenclature important
in this process; exact meaning to each species.
1. Linnaeus in the 18th century developed this system. System is binomial, and latinized. Genus
is the first part, species is the second part. First letter is capitalized of the genus; the whole thing
is italicised.
2. Phylogenetics continues placing the organism into a hierarchical structure. Similar genera go
into Families, similar families go into orders, similar orders go into Classes, similar classes go into
Phyla, and similar phyla go into Kingdoms. Many biologists now call for domains.
a. this classification process implies phylogeny, the evolutionary history of a species
b. these are commonly placed into a tree structure (Fig. 14.23)
3. Each proper name, D,K,D or P,C,O,F,G,S is called a taxon
4. There may be one, or many groups within each of the taxa.
B. Homology indicates common ancestry.
1. flippers on a whale evolved from legs
2. similar structures don't necessarily indicate homology. Homologs are different from analogs,
which have similar function.
a. convergent evolution - wings on a bat, a bird, an insect - analogous but not
homologous
C. Molecular biology is powerful tool in systematics
1. Protein comparisons – amino acid sequences – close match in sequence indicates common
gene from a common ancestor
2. RNA and DNA comparisons – nucleotide sequences – different parts of DNA mutate at
different rates, so we use it to see how distantly organisms are related.
D. Cladistic analysis - groups of an ancestor and all its descendents in phylogenetic classification
(Fig. 14.25 Platypus is more like ancestors of mammals than it is like other current mammals.
1. primitive characters - shared by all in the clade.
2. derived characters - homlogous features that have changed from an ancestral condition
E. Cladistics vs. classical systematics (Fig. 14.26) - Under debate
1. classical - tends to depend on subjective evaluation
3. cladistics - tends to depend on objective evaluation, testable hypotheses
III. Domains of life
A. (Fig.14.27, a and b) Arranging life into kingdoms is a work in progress, Kingdoms further grouped into
domains
Study Questions – Lesson Objectives/ch. 14
1. Describe the benefits and constraints of the use of the biological species concept
2. Describe 5 prezygotic barriers to interbreeding.
3. Describe 3 postzygotic barriers.
4. Explain how geologic processes fragment populations and lead to speciation.
5. Define adaptive radiation and explain why Galapagos finches are a good example.
6. Distinguish between sympatric and allopatric speciation and give examples.
7. Compare the gradualist model vs. punctuated equilibrium.
8. Briefly describe the history of life on earth, noting major eras, when they occurred, and which types of life
were most abundant.
9. Explain how radiometric dating is used to determine the age of rocks and fossils. Explain when carbon14
and potassium 40 are most useful.
10. Explain what continental drift is, and its significance to the history of life on earth.
11. Describe the process and consequences of plate tectonics.
12. Describe the causes, frequency and impact of mass extinctions.
13. Define exaptation, and give an example in a plant and an animal.
14. Explain how genes that are important in development are also important in evolution.
15. Explain why evolutionary trends are not goal oriented.
16. Explain the meaning of relationships in a phylogenetic tree.
17. Explain the goals of systematics. List the taxonomic groups used in systematics.
18. Compare and provide examples of homologous and analogous structures.
19. define these terms: clade, monophyletic, derived characters, primitive characters.
20. List and briefly describe the 3 domains. How are these related to the 5 kingdoms?