chapter 22 bewerktb (2)

video slideWelkom bij de module Evolutie!
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Natural Selection and Adaptation
Evolutionary biologist Ernst Mayr has dissected the logic of Darwin’s theory into three inferences based on five observations
Observation #1: For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully
Observation #2: Populations tend to be stable in size, except for seasonal fluctuations
Observation #3: Resources are limited
Inference #1: Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving
Observation #4: Members of a population vary extensively in their characteristics; no two individuals are exactly alike
Observation #5: Much of this variation is heritable
Inference #2: Survival depends in part on inherited traits; individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals
Inference #3: This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over generations
Darwin made two major points in his book:
Many current species are descendants of ancestral species
Natural selection is a mechanism for this evolutionary process
The Origin of Species
Challenged a worldview that had been prevalent for centuries
Concept 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species
To understand why Darwin’s ideas were revolutionary, we must examine them in relation to other Western ideas about Earth and its life
Untill the 19th century it was generally believed that species had remained unchanged since their creation
Although it was generally accepted that some species do change (artificial selection).
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
1798
1809
1830
1831–1936
1837
1844
1858
1859
1865
Fossils, Cuvier, and Catastrophism
The study of fossils helped to lay the groundwork for Darwin’s ideas
Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata
Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier
Cuvier advocated catastrophism, speculating that each boundary between strata represents a catastrophe
Theories of Gradualism
Gradualism is the idea that profound change can take place through the cumulative effect of slow but continuous processes
Geologists Hutton and Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today
This view strongly influenced Darwin’s thinking
Lamarck’s Theory of Evolution
Lamarck hypothesized that species evolve through:
use and disuse and
The mechanisms he proposed are unsupported with evidence
Lamarck’s Hypothesis of Evolution
Which of the following statements about Lamarck are accurate?
Lamarck thought evolution had occurred.
Lamarck proposed a mechanism for evolution.
Lamarck thought organisms became more complex because of an inner drive for complexity.
Lamarck was wholly wrong.
*
Answer: This question is designed to help students understand the history of evolutionary biology; it can also help give students a better idea of how science moves forward. Lamarck (and others) preceded Charles Darwin in thinking evolution had occurred (thus, option a is correct and option e is incorrect). Option b is also correct: Lamarck proposed a mechanism (use and disuse, and inheritance of acquired characteristics). However, Lamarck’s idea of a drive toward complexity has not been supported, so option c is incorrect.
Related to material on textbook page 454.
Concept 22.2: In The Origin of Species, Darwin proposed that species change through natural selection
After Darwin graduated as a clergyman he embarked on the Beagle in 1831.
In that time, most people believed that species couldn’t change.
Darwin observed many examples of adaptations: characteristics of organisms that enhance their survival and reproduction in specifiek environments.
LE 22-6
Cactus eater. The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp.
Seed eater. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground.
Insect eater. The green warbler finch (Certhidea olivacea) used its narrow, pointed beak to grasp insects.
In 1844, Darwin wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar
In June 1858, Darwin received a manuscript from Alfred Russell Wallace, who had developed a theory of natural selection similar to Darwin’s
Darwin quickly finished The Origin of Species and published it the next year
The Origin of Species
Evolution explains life’s unity and diversity
Natural selection is a cause of adaptive evolution
Descent with Modification
The phrase descent with modification summarized Darwin’s perception of the unity of life
The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past
In the Darwinian view, the history of life is like a tree with branches representing life’s diversity
Summary of Natural Selection
Natural selection is differential success in reproduction from interaction between individuals that vary in heritable traits and their environment
Natural selection produces an increase over time in adaptation of organisms to their environment
If an environment changes over time, natural selection may result in adaptation to these new conditions
Concept 22.3: Evolution is supported by an overwhelming amount of scientific evidence
Direct observations of evolutionary change
E.g. guppies or HIV virus
Homology
Fossil record
Natural Selection in Action
Two examples provide evidence for natural selection: the effect of differential predation on guppy populations and the evolution of drug-resistant HIV
Guppies: Smaller at sexual maturity than
those in “killifish pools”
The Evolution of Drug-Resistant HIV
The use of drugs to combat HIV selects for viruses resistant to these drugs
The ability of bacteria and viruses to evolve rapidly poses a challenge to our society
Homology, Biogeography, and the Fossil Record
Evolutionary theory provides a cohesive explanation for many kinds of observations
Homology is similarity resulting from common ancestry
Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor
Comparative embryology reveals anatomical homologies not visible in adult organisms
Vestigial organs are remnants of structures that served important functions in the organism’s ancestors
Molecular Homologies
Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor
Percent of Amino Acids That Are
Identical to the Amino Acids in a
Human Hemoglobin Polypeptide
Biogeography
Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution
Some similar mammals that have adapted to similar environments have evolved independently from different ancestors
The Fossil Record
The succession of forms observed in the fossil record is consistent with other inferences about the major branches of descent in the tree of life
The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record
Paleontologists have discovered fossils of many such transitional forms
What Is Theoretical about the Darwinian View of Life?
In science, a theory accounts for many observations and data and attempts to explain and integrate a great variety of phenomena

chapter 22 bewerktb (2)

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