Biology Abitur Lernzettel / Biology exam preparation –
Evolution and Natural Selection, Summary on Evolutionary
Processes and Theories
Table of Contents
Processes and Concepts of Evolution
Definition of evolution
Genetic variation within populations
Mutation and genetic change
Adaptation and selective pressure
Speciation and biodiversity
Theories of Evolution
Fixism and creationism
Catastrophism theory
Lamarckism and inheritance of acquired traits
Darwinism and natural selection
Synthetic theory of evolution
Genetic Basis of Evolution
Gene pool and allele frequencies
Microevolution and macroevolution
Importance of genetic diversity
Evolutionary Factors
Genetic variation
Mutations and their causes
Recombination during meiosis
Migration and gene flow
Genetic drift
Genetic Drift and Population Effects
Changes in allele frequencies
Population bottleneck
Founder effect
1
,Natural Selection
Definition and basic structure
Role of variation in populations
Struggle for existence and competition
Inheritance of advantageous traits
Adaptation over generations
Types of Natural Selection
Stabilizing selection
Directional selection
Disruptive selection
Sexual Selection
Intrasexual selection
Intersexual selection
Sexual dimorphism
Artificial Selection
Human-controlled breeding
Applications in agriculture and livestock
Effects on trait inheritance
2
,1.1 Processes and concepts of evolution
1. The structure of evolution
Description:
Evolution is the process in which heritable characteristics change over successive generations. It is
driven by special mechanisms such as natural selection, mutations, or genetic drift, which can affect
how organisms respond to their environment. Only populations or species within a population can
evolve but individuals do not evolve.
The main components of evolution:
Genetic variation: Differences in DNA sequences among individuals in a population, arising through
mutations, gene flow, and recombination. The main concept of evolution is that all individuals within
a species or population are genetically different from each other. Certain traits or genes carried by
some individuals may differ in other individuals of the same species or population.
Mutation: Random changes in the genetic material (DNA) that can introduce new traits. These
mutations can be beneficial, neutral, or harmful.
Natural selection: The process in which individuals with advantageous traits are more likely to
survive and reproduce, passing on their genes to the next generation. This leads to adaptation over
time, as more and more members of the species or population will develop the trait.
Genetic drift: Random changes in allele frequencies within a population, often affecting small
populations more strongly (e.g., bottleneck effect, founder effect).
Gene flow (migration): The movement of alleles between populations due to migration, which can
introduce new genetic variation.
Speciation: The formation of new species due to genetic divergence, often caused by geographic
isolation (allopatric speciation) or ecological differences (sympatric speciation).
Adaptation: The process by which a population becomes better suited to its environment through
evolutionary changes.
Selective pressure: Environmental factors (e.g., predators, climate, competition) that influence
which traits are beneficial for survival and reproduction.
Survival of the fittest: A concept where individuals best suited to their environment are more likely
to pass on their genes, influencing the genetic composition of future generations.
Convergent and divergent evolution: Convergent evolution occurs when unrelated species develop
similar traits due to similar environmental pressures. Divergent evolution occurs when species
develop different trait due to different environmental pressures but share a common ancestry.
3
, Functions of evolution:
Biodiversity creation:
Evolution is responsible for the great diversity of life forms on Earth. Diversity in ecosystems is
important as each species or population performs different roles and functions in the ecosystem.
This ensures resilience to environmental change, disease and other challenges. The ecosystem can
only remain stable if all of these organisms continue to perform their respective roles or functions.
Evolution ensures that specific or populations develop differently, so they all perform different roles
in the ecosystem.
Adaptation to the environment:
Organisms develop traits that increase their chances of survival and reproduction in specific habitats.
Adaptations can be structural (e.g., camouflage), physiological (e.g., toxin resistance), or behavioral
(e.g., migration patterns). Evolution causes species or populations to develop unique traits and
functions which are not present in other organisms. These traits may increase the survival chances
of the species or population, allowing them to reproduce successfully, obtain resources or maintain
vital functions.
2. The main theories of evolution
1. Fixism and creationism (teachings of species consistency)
Before the theory of evolution emerged in the 18th century, the teachings of species consistency
dominated. Accordingly, the diversity that exists between species was justified as creations of God
and remained immutable over time. The theory was divided into two terms known as creationism
(creation of God) and fixism (species do not vary over time). Thus, it was thought that species could
not change further and instead they remained constant as they were created by God. One of the
great proponents of this theory was Carl Linnaeus, who created the binomial classification of species.
This allowed an organism to be identified by its genus name and species name.
2. Catastrophism Theory
A very important fact that discredited fixism (species remaining constant) was the discovery of fossils
(evidence of living beings that no longer existed). Eventually, this gave way to the catastrophism
theory that justified the existence of fossils, but defended fixism. The theory was first proposed by
the naturalist Georges Cuvier, father of paleontology. Catastrophism states that the disappearance
of living beings was the result of a natural disaster, but the living beings that lived in the past were
created and remained unchanged. As a consequence of the disappearance of species due to natural
catastrophes, this creation process was repeated from time to time.
3. Lamarckism
Jean Baptiste Lamarck developed the first approaches to the theory of evolution. It is known as
transformation, Lamarckism or theory of the inheritance of acquired characters and was proposed
by Jean Baptiste de Lamarck. He argued that one species was transformed into another over time
and shared a common ancestor.
4
Evolution and Natural Selection, Summary on Evolutionary
Processes and Theories
Table of Contents
Processes and Concepts of Evolution
Definition of evolution
Genetic variation within populations
Mutation and genetic change
Adaptation and selective pressure
Speciation and biodiversity
Theories of Evolution
Fixism and creationism
Catastrophism theory
Lamarckism and inheritance of acquired traits
Darwinism and natural selection
Synthetic theory of evolution
Genetic Basis of Evolution
Gene pool and allele frequencies
Microevolution and macroevolution
Importance of genetic diversity
Evolutionary Factors
Genetic variation
Mutations and their causes
Recombination during meiosis
Migration and gene flow
Genetic drift
Genetic Drift and Population Effects
Changes in allele frequencies
Population bottleneck
Founder effect
1
,Natural Selection
Definition and basic structure
Role of variation in populations
Struggle for existence and competition
Inheritance of advantageous traits
Adaptation over generations
Types of Natural Selection
Stabilizing selection
Directional selection
Disruptive selection
Sexual Selection
Intrasexual selection
Intersexual selection
Sexual dimorphism
Artificial Selection
Human-controlled breeding
Applications in agriculture and livestock
Effects on trait inheritance
2
,1.1 Processes and concepts of evolution
1. The structure of evolution
Description:
Evolution is the process in which heritable characteristics change over successive generations. It is
driven by special mechanisms such as natural selection, mutations, or genetic drift, which can affect
how organisms respond to their environment. Only populations or species within a population can
evolve but individuals do not evolve.
The main components of evolution:
Genetic variation: Differences in DNA sequences among individuals in a population, arising through
mutations, gene flow, and recombination. The main concept of evolution is that all individuals within
a species or population are genetically different from each other. Certain traits or genes carried by
some individuals may differ in other individuals of the same species or population.
Mutation: Random changes in the genetic material (DNA) that can introduce new traits. These
mutations can be beneficial, neutral, or harmful.
Natural selection: The process in which individuals with advantageous traits are more likely to
survive and reproduce, passing on their genes to the next generation. This leads to adaptation over
time, as more and more members of the species or population will develop the trait.
Genetic drift: Random changes in allele frequencies within a population, often affecting small
populations more strongly (e.g., bottleneck effect, founder effect).
Gene flow (migration): The movement of alleles between populations due to migration, which can
introduce new genetic variation.
Speciation: The formation of new species due to genetic divergence, often caused by geographic
isolation (allopatric speciation) or ecological differences (sympatric speciation).
Adaptation: The process by which a population becomes better suited to its environment through
evolutionary changes.
Selective pressure: Environmental factors (e.g., predators, climate, competition) that influence
which traits are beneficial for survival and reproduction.
Survival of the fittest: A concept where individuals best suited to their environment are more likely
to pass on their genes, influencing the genetic composition of future generations.
Convergent and divergent evolution: Convergent evolution occurs when unrelated species develop
similar traits due to similar environmental pressures. Divergent evolution occurs when species
develop different trait due to different environmental pressures but share a common ancestry.
3
, Functions of evolution:
Biodiversity creation:
Evolution is responsible for the great diversity of life forms on Earth. Diversity in ecosystems is
important as each species or population performs different roles and functions in the ecosystem.
This ensures resilience to environmental change, disease and other challenges. The ecosystem can
only remain stable if all of these organisms continue to perform their respective roles or functions.
Evolution ensures that specific or populations develop differently, so they all perform different roles
in the ecosystem.
Adaptation to the environment:
Organisms develop traits that increase their chances of survival and reproduction in specific habitats.
Adaptations can be structural (e.g., camouflage), physiological (e.g., toxin resistance), or behavioral
(e.g., migration patterns). Evolution causes species or populations to develop unique traits and
functions which are not present in other organisms. These traits may increase the survival chances
of the species or population, allowing them to reproduce successfully, obtain resources or maintain
vital functions.
2. The main theories of evolution
1. Fixism and creationism (teachings of species consistency)
Before the theory of evolution emerged in the 18th century, the teachings of species consistency
dominated. Accordingly, the diversity that exists between species was justified as creations of God
and remained immutable over time. The theory was divided into two terms known as creationism
(creation of God) and fixism (species do not vary over time). Thus, it was thought that species could
not change further and instead they remained constant as they were created by God. One of the
great proponents of this theory was Carl Linnaeus, who created the binomial classification of species.
This allowed an organism to be identified by its genus name and species name.
2. Catastrophism Theory
A very important fact that discredited fixism (species remaining constant) was the discovery of fossils
(evidence of living beings that no longer existed). Eventually, this gave way to the catastrophism
theory that justified the existence of fossils, but defended fixism. The theory was first proposed by
the naturalist Georges Cuvier, father of paleontology. Catastrophism states that the disappearance
of living beings was the result of a natural disaster, but the living beings that lived in the past were
created and remained unchanged. As a consequence of the disappearance of species due to natural
catastrophes, this creation process was repeated from time to time.
3. Lamarckism
Jean Baptiste Lamarck developed the first approaches to the theory of evolution. It is known as
transformation, Lamarckism or theory of the inheritance of acquired characters and was proposed
by Jean Baptiste de Lamarck. He argued that one species was transformed into another over time
and shared a common ancestor.
4
