Chapter 11 Evidence of Evolution Pg. 190
- Darwin’s observations of the natural world led him to propose
that evolution could occur by way of a process called natural
- There is mow much evidence in support of evolution that comes
from fossils, the geologic record and radioactive dating of
- Further evidence comes from comparative studies of anatomy
and biochemistry of different lineages that have helped us to
identify patterns of change through time.
- NATURAL SELECTION ONLY ACTS ON A TRAIT IF IT IS
What DOES the SELECTING of traits that will pass into the next
generations in the greatest frequency?? – the ENVIRONMENT -
individuals show variation and the environment selects the most FIT.
The most fit individuals in evolutionary terms, in natural selection
terms – are simply those that leave the most fertile offspring, no
matter how healthy an individual might be during its life or how long it
lives, it is how many fertile offspring that individual contributes to
the next generation that counts, in evolutionary terms fitness means
Another important point to note is that while natural selection
certainly acts on an individual, it is actually POPULATIONS that evolve,
evolution is a population based theory.
1 11.2 Early Beliefs, Confusing Discoveries
biogeography – study of patterns I the geographic distribution of
species and communities
mass extinction – Simultaneous loss of many lineages from Earth
comparative morphology – the scientific study of anatomical patterns
in body plans
fossil – physical evidence of an organism that lived in the ancient past
1. Expeditions by nineteenth century explorers yielded increasingly
detailed observation of nature.
2. Geography, biogeography, and comparative morphology of
organisms and their fossils led to new ways of thinking about the
Take Home Message
How did observations of the natural world change our thinking in the
3. Increasingly extensive observations of nature in the nineteenth
century did not fit with prevailing belief systems
4. Cumulative findings from biogeography, comparative
morphology ad geology let naturalists to question traditional
ways of interpreting the natural world.
2 11.3 A flurry of New Theories pg 192
lineage – line of descent
evolution – change in a line of descent (lineage)
adaptation – (adaptive trait) – A heritable trait that enhances an
individual’s fitness in a particular environment
artificial selection – process whereby humans alter traits of a domestic
species by selective breeding over generations
fitness – degree of adaptation to an environment, as measured by an
individual’s relative genetic contribution to future generations. In other
words how many fertile offspring .
natural selection – differential survival and reproduction of individuals
of a population based on differences in shared, heritable traits. Driven
by environmental pressures.
1. Prevailing belief systems may influence interpretation of the
underlying cause of a natural event.
2. Nineteenth century naturalists attempted to reconcile traditional
belief systems with physical evidence of evolution, or change in a
lineage over time.
3. Humans select desirable traits in animals by selective breeding, or
4. Charles Darwin and Alfred Wallace independently came up with
a theory of how environments also select traits, stated here in
modern terms: A population tends to grow until it exhausts
environment resources. As that happens competition for those
resources intensifies among the population’s individuals
5. Individuals with forms of shared, heritable traits that make them
more competitive for the resources tend to produce more
6. Thus adaptive traits (adaptations) that impart greater fitness
to an individual become more common in a population over
3 7. The process in which environmental pressures result in the
differential survival and reproduction of individuals of a
population is called natural selection.
8. It is one of the processes that drives evolution.
Take Home Message
How did the way that naturalists thought about the history of life
change in the nineteenth century?
1. Evidence found in the 1800s led to the idea that Earth and the
species on it had changed over very long spans of time. This
idea set the stage for Darwin’s theory of evolution by natural
2. Natural selection is a process in which individuals of a
population survive and reproduce with differing success
depending on the details of their shared heritable traits.
3. Traits favoured in a particular environment are adaptive. An
adaptive trait increases the chances that an individual bearing it
will survive and reproduce.
4 Principles of Natural Selection, in Modern Terms Fig. 11.1 page 195
Observations about populations
- Natural populations have an inherent reproductive capacity to
increase in size over time
- As a population expands, resources that are used by its
individuals (such as food and living space) eventually become
- When resources are limited, the individuals of a population
compete for them
Observations about Genetics
- Individuals of a species share certain traits
- Individuals of a natural population vary in the details of those
- Shared traits have a heritable basis, in genes. Slightly different
forms of those genes (alleles) give rise to variation in shared traits
- A certain form of a shared trait may make its beare