Samenvatting vanal het materiaal uit Campbell's Biology: a global approach voor de eerste deeltoets, gericht op het eerstejaars vak Evolutie en biodiversiteit wat op de universiteit in Utrecht gegeven word.
DEELTOETS 1: EVOLUTIE EN
BIODIVERSITEIT
Biology: A Global Approach (12th edition)
Contents:
Chapter 21: How evolution works?
Chapter 22: Phylogenetic reconstruction
Chapter 23: Microevolution
Chapter 24: Species and speciation
Chapter 25: Macroevolution
Chapter 34: Vertebrates (only paragraph 6 and 7)
Chapter 52: Behavioural ecology
Chapter 56: Conservation and global ecology
Lenore van Vliet
09/2021
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21. How evolution works
21.1 THE DARWINIAN REVOLUTION CHALLENGED TRADITIONAL VIEWS OF A YOUNG
EARTH INHABITED BY UNCHANGING SPECIES
Endless forms most beautiful
Shared features illustrate the unity of life, since all organisms share characteristics, Darwin’s theory
illustrated 3 key points:
1. Organisms are well suited for life in their environments
2. The many shared characteristics of life
3. The rich diversity of life
Darwin eventually concluded that life evolves over time!
Evolution = descent with modification
Or also known as change in the genetic composition of a population from generation to generation.
This can be related to two ways we can look at evolution:
Pattern --> data from many different disciplines
Process --> the mechanisms that cause the observed pattern of change = representing the
natural causes of the natural phenomena we observe.
The power of evolution as a unifying theory is its ability to explain and connect a vast array of
observations about the living world.
--> This theory continues to be tested by examining whether or not it can account for new
observations and experimental results.
Scala naturae and classification of species
- Aristotle => recognized certain affinities among organisms and concluded that life-forms
could be arranged on a ladder of increasing complexity later known as the Scala naturae.
- Linnaeus => developed a two part/binomial system for naming species using a nested
classification system, but he did not ascribe the resemblances among species.
- Cuvier => observed that from one layer of stone to the next species disappeared and
appeared. Coming to the conclusion that extinctions are common because each boundary
between strata represents a sudden catastrophic event.
- Hutton => proposed that earth’s geologic features could be explained by gradual
mechanisms.
- Lyell => Used Hutton’s thinking to state that the same geologic mechanisms are operating
today as in the past and at the same rate.
- Lamarck => proposed that life evolves as environments change
Ideas about change over time
Fossils (= the remains or traces of organisms from the past) contain a lot of evolutionary data that
Darwin could use for his theory of evolution through natural selection, agreeing that if geologic
change results from slow continuous processes rather than sudden events, then earth must be much
older than the widely accepted age of a few thousand years.
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Lamarck’s hypothesis of evolution
The incorrect mechanism Lamarck proposed is what he is most well-known for: He compared living
species with fossil forms and explained his findings using two principles widely accepted during his
time:
--> Use and disuse = the idea that parts of the body that are used extensively become larger
and stronger, while those that are not used deteriorate.
--> Inheritance of acquired characteristics = an organism could pass modifications to its
offspring.
This led to Lamarck concluding that evolution happens because organisms have an innate drive to
become more complex.
Darwin rejected this idea but he did agree that variation was introduced into the evolutionary
process in part by inheritance of acquired characteristics.
21.2 DESCENT WITH MODIFICATION BY NATURAL SELECTION EXPLAINS THE
ADAPTATIONS OF ORGANISMS AND THE UNITY OF LIF E
Darwin went on a voyage around the world during which he found fossils of ocean organisms high in
the Andes, and this reinforced what he had learned from Lyell: physical evidence did not support the
traditional view that the earth was only a few thousand years old.
Many examples of adaptations and inherited characteristics of organisms that enhance survival and
reproduction in specific environments, which led him to ask the question: Could a new species arise
from an ancestral form by the gradual accumulation of adaptations to a different environment?
Darwin realized that explaining adaptations was essential to understanding evolution. His
explanation of how adaptations arise centered on natural selection (= a process in which individuals
that have certain inherited traits tent to survive and reproduce at higher rates than do other
individuals because of those traits).
--> Darwin’s book: The origin of species and its proponents have convinced most scientists
that life’s diversity is the product of evolution.
Ideas from the origin of species
Natural selection explains three broad observations about nature: the unity of life, the diversity of
life and the striking ways in which organisms are suited for life in their environments.
- Descent with modification = Darwin’s view of life --> As the descendants of an ancestral
organism lived in various habitats they gradually accumulated diverse modifications or
adaptations that fit them to specific ways of life.
It has led to the rich diversity of life, so he figured that the history of life can be viewed as a
tree with multiple branching’s from a common trunk.
- Artificial selection, natural selection and adaptation = Humans have modified species over
many generations by selecting and breeding individuals that possess desired traits (=
artificial selection)
Darwin stated that a similar process occurs in nature:
Observation 1: members of a population often vary in their inherited traits
Observation 2: all species can produce more offspring than their environment can
support and many of these offspring fail to survive and reproduce.
Inference 1: individuals whose inherited traits give them a higher probability of
surviving and reproducing in a given environment tend to leave more
offspring than do other individuals.
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Inference 2: this unequal ability of individuals to survive and reproduce will lead to
the accumulation of favourable traits in the population over generations.
Darwin similarly realized that the capacity to over reproduce was typical of all species, since
an organism’s heritable traits can influence its own performance but also how well its
offspring can cope with environmental challenges.
When advantages increase the number of offspring that survive and reproduce, the traits that are
favoured will likely appear in greater frequency in the next generation.
--> Artificial selection can bring about dramatic change in a relatively short amount of time.
Advantageous variations will gradually accumulate in the population while less favourable variations
will diminish leading to an increasing degree to which organisms are well suited for life in their
environment.
Key features of natural selection:
- Natural selection is a process in which individuals that have certain heritable traits survive
and reproduce at a higher rate
- Over time natural selection can increase the frequency of adaptations that are favourable in
a given environment
- If an environment changes natural selection may result in adaptations to these new
conditions and can ultimately result in the rise of a new species
Although natural selection occurs through interactions between individual organisms and their
environment, individuals do not evolve! Populations do!
Natural selection can only amplify or diminish inheritable traits that differ among the individuals of a
population.
Environmental factors can vary from place to place and over time --> a trait that is favourable in one
place and at one time may be useless in other places and other times.
21.3 EVOLUTION IS SUPPORTED BY AN OVERWHELMING AMOUNT OF SCIENTIFIC
EVIDENCE
There are instances in which key evidence for Darwin’s theory of evolution were lacking. There was a
significant chunk of fossils missing that proved earlier groups gave rise to new groups. 4 types of
data document the pattern of evolution and illuminate how it occurs:
1. Direct observations
Herbivores often have adaptations that help them feed efficiently of their primary food sources,
which demonstrates that natural selection can cause rapid evolution in a wild population.
2. Homology
Analysation of similarities among different organisms. Characteristics present in an ancestral
organism are altered in its descendants over time as they face different environmental conditions.
Underlying similarity with a different function resulting from common ancestry is known as
homology.
Closely related species share the features used to determine their relationship, but they also share
many other features. Some of the shared features make little sense except in the light of evolution.
--> Striking anatomical resemblances would be highly unlikely if these structures had arisen
anew in each species.
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