Unit 1:
Evolution by Natural Selection
Evolution
● A general term defined as change over time: chemical, matter, solar systems or
language.
Biological evolution
● Can be described as genetic change in a population that is inherited over successive
generations due to natural selection, ultimately resulting in a new species
Macro -Evolution
● The development of new life or species from earlier life forms over many
generations (extended geological periods) 1
● Speciation2 forms the basis of macro-evolution, where new sepsis develops from
existing species over time
Micro-Evolution
● The variation that occurs within a species.
● Small changes originate in the gene pools3, that result in small changes in the
genotype of the species
● The changes are passed on to the o spring
1
refers to the idea that over long periods of time, genetic mutations, natural selection, and
other processes can lead to the formation of new species, genera, and higher taxonomic
groups from earlier forms of life.
2
Speciation is the process by which new species arise from existing ones. In other words, it
is the evolutionary process by which populations of a single species become isolated from
each other and diverge over time, eventually becoming distinct and reproductively isolated
groups that can no longer interbreed.
3
A gene pool refers to the complete set of genes, including all the di erent alleles, present
in a population of interbreeding organisms. In other words, it is the sum total of all the
genetic information carried by all the individuals within a population. Each gene pool
consists of all the genetic variations present in a population, including mutations,
recombinations, and other sources of genetic variation.
, Micro-evolution refers to the evolutionary changes that occur within a population
or a species over a relatively short period of time, usually within a few generations
or centuries. Micro-evolutionary changes can be observed directly and involve
small-scale genetic changes, such as variations in allele frequencies, genetic drift,
gene flow, and natural selection.
For example, the evolution of antibiotic resistance in bacteria, the variation in beak size
in finches, or the development of pesticide resistance in insects are all examples of
micro-evolutionary changes.
Macro-evolution refers to the large-scale evolutionary changes that occur over
geological time scales, usually over millions of years, and that result in the
diversification of life into di erent species, genera, families, and other taxonomic
groups. Macro-evolutionary changes involve the accumulation of many small-scale
micro-evolutionary changes over long periods of time, resulting in the emergence
of new traits, body structures, and forms of life.
For example, the evolution of birds from theropod dinosaurs, the origin of mammals
from reptilian ancestors, and the diversification of flowering plants are all examples of
macro-evolutionary changes.
Hypothesis or Theory?
● Hypothesis
- Informed or educated assumption
- Provides a proposed solution/explanation to a problem/phenomenon
- It's tested by lots of experiments or by repeated observation
● Theory
- Well-substantiated explanation or hypothesis that is well substantiated
- Based on scientific evidence
- Usually tested and confirmed by independent groups of researchers
- It develops and changes or is replaced as new evidence is discovered
Evolution is considered a theory, as it's based on a series of hypotheses and tested and verified
over time (the time frame of millions of years ago is not easily observable)
Origin of Ideas About Origins
● Evolutionists believe this process led to the enormous biodiversity that currently
exists on earth
● Evolution doesn't explain the origin of life
, Evidence of Evolution
The scientific theory of evolution emerged from and is explained by di erent lines
of evidence that are contributed by many scientists
➔ Fossil Records
➔ Modification by decent
➔ Biogeography
➔ Genetics
➔ Other…
● Fossil records
➢ Photo of Ammonite
➢ Provide evidence of the history of the
extinct organisms on earth
➢ Gives an indication of climate and
environment millions of years ago
➢ The fossil record is the accumulation of
all listed and known fossils of di erent ages that have been discovered by
palaeontologists worldwide; paleoanthropologist is specilised in humans
fossils
➢ Few individuals fossilise - possibly because they are soft-bodied and
decompose after death, and the structure is not preserved
➢ Verry-specific conditions (rapid burial, high pressure, low oxygen) are
essential for fossilisation to occur
➢ The fossil record is a record of those organisms that were fossilised, but,
they are incomplete and not an indication of all organisms that existed
during that time
➢ The fossil record provides information about extinct species as well as ones
still living today
➢ Scientists expect to find earlier, simpler fossils in deeper older rocks layers
➢ Scientists expect to find recent more complex fossils in upper more recent
rock layers
➢ It indicates what order evolution took place
➢ The age of the fossil can be determined by the age of the rock
➢ Older rock strata display less biodiversity, this shows the increase in
biodiversity over time
, A transitional fossil is a fossilized remain or impression of an organism that exhibits
characteristics of both ancestral and descendant groups. It provides evidence for the
evolutionary transition between di erent species or groups of organisms. ese fossils capture
intermediate features, showing the gradual changes that occurred during the evolution of a
particular lineage.
Archaeopteryx is a classic example of a transitional fossil. It is an extinct bird-like dinosaur
that lived approximately 150 million years ago during the Late Jurassic period. Archaeopteryx
exhibits characteristics of both dinosaurs and birds, making it a crucial link in the evolutionary
transition from reptiles to birds.
Several key features of Archaeopteryx demonstrate its transitional nature. It had the skeletal
structure of a reptile, including a long bony tail, teeth, and claws on its wings. However, it also
possessed bird-like features such as feathers and wings adapted for flight. Archaeopteryx had a
mix of reptilian and avian characteristics, representing an intermediate stage in the evolution of
birds from dinosaurs.
e discovery of Archaeopteryx in the late 19th century provided strong evidence for the
evolutionary relationship between birds and reptiles. Its existence supported the theory of
evolution by showing a clear transition between two distinct groups of organisms. e presence
of feathers in Archaeopteryx also highlighted the evolutionary significance of feathers as a
feature that evolved for purposes other than flight, such as insulation or display, before being
adapted for flight in later bird species.
Evolution by Natural Selection
Evolution
● A general term defined as change over time: chemical, matter, solar systems or
language.
Biological evolution
● Can be described as genetic change in a population that is inherited over successive
generations due to natural selection, ultimately resulting in a new species
Macro -Evolution
● The development of new life or species from earlier life forms over many
generations (extended geological periods) 1
● Speciation2 forms the basis of macro-evolution, where new sepsis develops from
existing species over time
Micro-Evolution
● The variation that occurs within a species.
● Small changes originate in the gene pools3, that result in small changes in the
genotype of the species
● The changes are passed on to the o spring
1
refers to the idea that over long periods of time, genetic mutations, natural selection, and
other processes can lead to the formation of new species, genera, and higher taxonomic
groups from earlier forms of life.
2
Speciation is the process by which new species arise from existing ones. In other words, it
is the evolutionary process by which populations of a single species become isolated from
each other and diverge over time, eventually becoming distinct and reproductively isolated
groups that can no longer interbreed.
3
A gene pool refers to the complete set of genes, including all the di erent alleles, present
in a population of interbreeding organisms. In other words, it is the sum total of all the
genetic information carried by all the individuals within a population. Each gene pool
consists of all the genetic variations present in a population, including mutations,
recombinations, and other sources of genetic variation.
, Micro-evolution refers to the evolutionary changes that occur within a population
or a species over a relatively short period of time, usually within a few generations
or centuries. Micro-evolutionary changes can be observed directly and involve
small-scale genetic changes, such as variations in allele frequencies, genetic drift,
gene flow, and natural selection.
For example, the evolution of antibiotic resistance in bacteria, the variation in beak size
in finches, or the development of pesticide resistance in insects are all examples of
micro-evolutionary changes.
Macro-evolution refers to the large-scale evolutionary changes that occur over
geological time scales, usually over millions of years, and that result in the
diversification of life into di erent species, genera, families, and other taxonomic
groups. Macro-evolutionary changes involve the accumulation of many small-scale
micro-evolutionary changes over long periods of time, resulting in the emergence
of new traits, body structures, and forms of life.
For example, the evolution of birds from theropod dinosaurs, the origin of mammals
from reptilian ancestors, and the diversification of flowering plants are all examples of
macro-evolutionary changes.
Hypothesis or Theory?
● Hypothesis
- Informed or educated assumption
- Provides a proposed solution/explanation to a problem/phenomenon
- It's tested by lots of experiments or by repeated observation
● Theory
- Well-substantiated explanation or hypothesis that is well substantiated
- Based on scientific evidence
- Usually tested and confirmed by independent groups of researchers
- It develops and changes or is replaced as new evidence is discovered
Evolution is considered a theory, as it's based on a series of hypotheses and tested and verified
over time (the time frame of millions of years ago is not easily observable)
Origin of Ideas About Origins
● Evolutionists believe this process led to the enormous biodiversity that currently
exists on earth
● Evolution doesn't explain the origin of life
, Evidence of Evolution
The scientific theory of evolution emerged from and is explained by di erent lines
of evidence that are contributed by many scientists
➔ Fossil Records
➔ Modification by decent
➔ Biogeography
➔ Genetics
➔ Other…
● Fossil records
➢ Photo of Ammonite
➢ Provide evidence of the history of the
extinct organisms on earth
➢ Gives an indication of climate and
environment millions of years ago
➢ The fossil record is the accumulation of
all listed and known fossils of di erent ages that have been discovered by
palaeontologists worldwide; paleoanthropologist is specilised in humans
fossils
➢ Few individuals fossilise - possibly because they are soft-bodied and
decompose after death, and the structure is not preserved
➢ Verry-specific conditions (rapid burial, high pressure, low oxygen) are
essential for fossilisation to occur
➢ The fossil record is a record of those organisms that were fossilised, but,
they are incomplete and not an indication of all organisms that existed
during that time
➢ The fossil record provides information about extinct species as well as ones
still living today
➢ Scientists expect to find earlier, simpler fossils in deeper older rocks layers
➢ Scientists expect to find recent more complex fossils in upper more recent
rock layers
➢ It indicates what order evolution took place
➢ The age of the fossil can be determined by the age of the rock
➢ Older rock strata display less biodiversity, this shows the increase in
biodiversity over time
, A transitional fossil is a fossilized remain or impression of an organism that exhibits
characteristics of both ancestral and descendant groups. It provides evidence for the
evolutionary transition between di erent species or groups of organisms. ese fossils capture
intermediate features, showing the gradual changes that occurred during the evolution of a
particular lineage.
Archaeopteryx is a classic example of a transitional fossil. It is an extinct bird-like dinosaur
that lived approximately 150 million years ago during the Late Jurassic period. Archaeopteryx
exhibits characteristics of both dinosaurs and birds, making it a crucial link in the evolutionary
transition from reptiles to birds.
Several key features of Archaeopteryx demonstrate its transitional nature. It had the skeletal
structure of a reptile, including a long bony tail, teeth, and claws on its wings. However, it also
possessed bird-like features such as feathers and wings adapted for flight. Archaeopteryx had a
mix of reptilian and avian characteristics, representing an intermediate stage in the evolution of
birds from dinosaurs.
e discovery of Archaeopteryx in the late 19th century provided strong evidence for the
evolutionary relationship between birds and reptiles. Its existence supported the theory of
evolution by showing a clear transition between two distinct groups of organisms. e presence
of feathers in Archaeopteryx also highlighted the evolutionary significance of feathers as a
feature that evolved for purposes other than flight, such as insulation or display, before being
adapted for flight in later bird species.
