chapter 9,10 and 11 Flashcards
index fossil
A fossil that, due to the short existence and wide geographic distribution of its species, is used to define and quickly identify particular geographical timeframes.
transitional fossil
A fossil that exhibits characteristics that are common to both its ancestor group and its descendant group.
Cambrian explosion
A key biological event in Earth’s history approximately 535 million years ago when practically all major animal phyla started appearing in the fossil record.
permineralisation
A process of fossilisation where mineral deposits, typically carried by water, fill the spaces within organic tissue and form rock-like relics of an organism.
sedimentary rock
Rock that has formed through the accumulation of sediment and hardened under pressure.
geological time
A system for chronologically dating different sedimentary rock strata using known time frames, such as periods, eras, or eons.
law of fossil successsion
The law of fossil succession underpins relative dating techniques, and suggests that fossils closest to the surface must be younger than those that are found below it.
Cardon dating
halflife of carbon 14 is 5730
Homologous structures
features
present in two or more species
that may look and function very
differently in each species, but are
derived from a common ancestor
gene pool
the complete set of
alleles present within a particular
population
mutagen
give example
an agent that can cause
mutations in DNA
ionising radition can induce mutation
can break sugar phosphate bonds in DNA, or change nitrogenous bases in DNA.
also indirectly ionside by causing oter molecules in a call, produce free radicals which can interact with other molecules and damage DNA
chemical induce mutation
Reactive oxygen species (ROS), such as free radicals.
Heavy etals can cause sugar phosphate backbone to break
Deaminating agents can convert nitrougenous bases, such as c to u
Point mutations
Point mutations describe changes to a single nucleotide in a gene
can be further broken
down into silent, missense, and nonsense mutations
Silent mutation
Substitution mutations that have no effect on the resulting amino acid sequence. Due to the degenerate nature of the genetic code, multiple different codons code
for the same amino acid and, therefore, despite a change to the original DNA
sequence, the same amino acid is incorporated into the protein
Missense mutation
Substitution mutations which code for a different amino acid, altering the primary structure of the polypeptide. This in turn affects the folding of the polypeptide and could alter the functioning of the protein.
Nonsense mutation
Substitution mutations which prematurely end the translation of a gene’s mRNA. Codes for a stop codon, gene will not be completely transalated, polypeptide prematuraly stops making ot too small to function
Frameshift mutation
Addition or deletion of one or two nucleotides, which alters the reading frame of
all the following nucleotides. The reading frame is how DNA or mRNA is divided
into triplets or codons respectively. Since the reading frame is shifted in frameshift mutations, all following codons and the amino acids they code for are affected, which can cause major disruptions to the structure and function of the protein.
Block mutations
a mutation that
affects a large part of DNA, or an
entire gene
aneuploidy
when a cell or
organism varies in the usual amount of chromosomes in its
genome by the addition or loss of a chromosome
polyploidy
when an organism
contains additional sets of
chromosomes in its genome
Block mutations-deletion,
duplication, inversion
deletion- removal of a
section of DNA.
Duplication-replication of a
section of DNA,
lengthening the DNA.
Inversion- reversal of a
section of DNA.
Translocation-switching of two sections of DNA on
different chromosomes
I
allele
an alternate form of a gene
natural selection
key machanism of evolution.It is the differential survival and reproduction of invdividuals in a species due to selection advantage and disadvantage conffered by heritable differences in their phenotypes.
4 conditions of natural selection
Variation- Individuals in a population vary genetically, which leads to phenotypic differences.
Selection pressure-An environmental selection pressure impacts the survivability of organisms within a population and their ability to reproduce.
Selective advantage-Individuals with phenotypes that are fitter or more advantageous under the environmental selection pressure are conferred a selective advantage, allowing
them to survive and reproduce more successfully.
Heritability-must be heritable
environmental selection
pressure
a factor in the
environment (e.g. limited
resources, deforestation, changing temperature, predation) that impacts an organism’s ability to survive and reproduce
gene flow
the flow of alleles in
and out of a population due to the migration or interbreeding of individuals between two
populations
immigration vs emmigration
immigration- the movement into a
population
emigration- the movement out of a population
species
a group of individuals
who are able to breed with each other and produce viable and fertile offspring.
Speciation is the process by which populations genetically diverge until they become
distinct species.
allopatric speciation
the geographic (isolation) separation of a population from a parent population resulting in the formation of a new species. (no flow)
v-variation
I-isolation
S-selection pressure
A-Selective advantage
T-time
A-accumalation of mutations, they cant reproduce anymore, different species have been created
Isolation mechanism-
Pre-reproducive
Geographical – individuals may not be able to interact with each other due to
separation by barriers (e.g. body of water)
Ecological – individuals may inhabit different ecological niches or habitats so they do not interact with each other.
Temporal– the time of the day or year when individuals are ready to breed may differ.
Behavioural – the type of mating behaviours, such as mating call, of individuals
may vary.
Structural– the physical characteristics of individuals may drastically vary, physically preventing breeding
species
a group of individuals
who are able to breed with each
other and produce viable and
fertile offspring
Post-reproductive
Gamete mortality– the sperm may be unable to penetrate the ovum for
fertilisation.
Zygote mortality – fertilisation may occur and a zygote may be formed,
however, it will not survive.
Hybrid sterility – a viable offspring may be formed and may survive until
adulthood, but will not be fertile
Galápagos finches
The Galápagos Islands are a collection of 19 islands situated in the Pacific Ocean west of Ecuador. Each of the 19 islands represents a specific ecological niche, each with its own different selection pressures and species.
beak shape change according to the food they consumed
Galápagos finches allopatric sepciation
It has been hypothesised that the formation of these different species of Galápagos finches
has largely been a result of allopatric speciation. This is because each of the islands is separated by the ocean, preventing gene flow. Moreover, different islands have different
food sources and each island presents its own selection pressures, selecting for different
phenotypes (such as beak shape) and allowing for genetic differences to accumulate. Subsequently, once sufficient differences accumulated and viable and fertile offspring
could no longer be produced through interbreeding, new species of finches were formed
Sympatric speciation
Sympatric speciation involves the formation of a new species in populations located in the
same geographical location.
different selection pressure act on different phenotypes within a population.
also arise from g
enetic abnormalites
Howea palms
While Howea belmoreana
inhabits neutral and acidic soils (low pH), Howea forsteriana inhabits a region of alkaline soil (high pH) known as calcarenite.This led researchers to suggest that Howea forsteriana diverged from its sister species Howea belmoreana after the initial population colonised the alkaline soil, which acted as a selection pressure.Flowering time acted as a isolation mechanism
gene drift
Genetic drift involves changes to a population’s allele frequencies due to sudden and random occurrences.
Bottleneck effect
The bottleneck effect occurs when a large portion of a population is wiped out by a random event such as a natural disaster. These events can dramatically decrease the
population size, significantly impacting allele frequencies. Due to the severe reduction in
population size, many individuals carrying unique alleles can be lost. Therefore, the new population has lower genetic diversity than the pre-disaster population
Founder effect
The founder effect occurs when a small unrepresentative sample of individuals separates
from a larger population to colonise a new region and start a new population
selective breeding
the changing
of a population’s gene pool due
to humans altering the breeding
behaviour of animals and plants to develop a selected trait.
Also known as artificial selection natural selection a mechanism
through which organisms that are better adapted to their environment have an increased chance of surviving and passing
on their alleles
The requirements for selective breeding
Variation, Selection pressure- Direct human intervention places an artificial selection pressure upon a population
of individuals, only allowing certain individuals with desirable traits to breed together.
Heritability
effect of selective breeding
If poor breeding practices are implemented, selective breeding can cause a humaninduced genetic bottleneck. This is because in large populations, only a small percentage of individuals express traits desired by humans.
Additionally, reduced genetic diversity can lead to increased inbreeding, which can
increase the prevalence of deleterious alleles, and a lower adaptive potential. These two effects are detrimental to the survival of a population.
antibiotic resistance
(1) outline
that variation exists, (2) identify the presence of a new selection pressure (exposure to antibiotic), (3)
identify the group that is conferred an advantage, and (4) highlight the increased heritability of the
antibiotic-resistant alleles.
Variation and the emergence of new alleles conferring resistance against antibiotics is
facilitated largely by mutations. Through mutations, new alleles can help bacteria develop
mechanisms which increase their ability to combat the action of antibiotics. Some of these
mechanisms, such as the impermeability of an antibiotic due to a modified cell wall or the
active efflux of an antibiotic out of a bacteria
Viral antigenic drift and shift
antigenic drift, which involves small and gradual changes in the genes encoding for viral surface antigens
antigenic shift, which involves sudden and significant changes in the genes encoding for viral surface antigens. This commonly occurs when two or more different strains
of a virus combine when coinfecting the same host to form a completely new subtype through a process known as viral recombination
fossilisation steps
Remnants of an organism are rapidly covered by sediment, meaning that the dead organism is not exposed to oxygen, microorganisms, and other disturbances that would
increase its rate of decomposition.
Over time, sediment layers build upon each other and compact, layer by layer, until pressure cements them together to form sedimentary rock
Within this rock, the fossilised remains can take many forms, including a
permineralised , mould, or cast fossil.
transitional fossils
a fossil that shows traits that are common to both its ancestral group and its descendant group. They are particularly important when the descendant species is physically very distinct from the ancestral species, such that the transitional fossil can help demonstrate evolutionary changes between the two
carbon-14
Radioisotopes are unstable elements that will break down over time into a more stable product. For instance, carbon-14 (a radioisotope) will break down into nitrogen-14.
While these radioisotopes can break down at any point, on average the rate of breakdown is constant and can be modelled. One of the ways in which we model this breakdown is by calculating the half-life of that radioisotope.
Half-life describes the amount of time before half of the mass of a radioisotope
is broken down into predictable and stable products. For example, carbon-14 is a
radioisotope that has a half-life of 5 730 years. This means that after 5 730 years of anorganism’s death, half of its carbon-14 atoms will have broken down into nitrogen-14
atoms
Radioisotopes series
Carbon-14 – nitrogen-14,
5 730 years
Uranium-235 – lead-207, 700 million years
Potassium-40 – argon-40 , 1.3 billion years
Principle of Faunal Succession:
The law of fossil succession states that because sedimentary rock is formed by the accumulation of sedimentary layers on top of each other, the fossils closer to the surface
must be younger than those that are found below them . This means that we
can assign fossils a relative age – an approximate age based on the position of the fossil
compared to other fossils
Principle of Correlation
atching rock layers from different locations based on similarities in their fossil content or other characteristics.
index fossil
physically distinctive
have had a large population
have existed in many geographical areas
only lived within a known short period of time.
Homologous structures
features present in two or more species that may look and function very differently in each species, but are derived from a common ancestor
Homologous structures are physical evidence of divergent evolution, the evolutionary process where two or more populations of a single species accumulate enough genetic differences to be classified as different species.
divergent evolution
the process in which a common ancestor evolves into two or more descendant species
Analogous structures
Analogous structures are structures that serve similar biological functions but are not derived from a common ancestor. Analogous structures are evidence of convergent evolution in which two or more distantly related species can be seen to have independently evolved similar traits to adapt to similar
environments and selection pressures.
vestigial structures
features that have lost all or most of their usefulness as a result of evolution by natural selection, easy method to infer relatedness between species.
Molecular homology
Molecular homology is the study of the similarities between organisms at a DNA and
amino acid level. There are many different types of proteins present in the body, but when
studying amino acid sequence similarities, we analyse proteins from conserved genes
which are found in a number of different species.
DETERMINING RELATEDNESS USING MITOCHONDRIAL DNA
mtDNA is almost 17 000 nucleotides long in humans and contains 37 genes, compared to the over 24 000 genes in our nuclear DNA.
The mutation rate in mtDNA is much higher than in nuclear DNA. This means that for very closely
related species, the mutation rate still ensures that there are enough differences in DNA sequences for us to compare.
There is no recombination (mixing of DNA between homologous chromosomes during meiosis) in mtDNA because it’s only inherited from the mother. This means that mtDNA remains unchanged from
generation to generation, which makes it easier to trace past ancestors.
Hominoids
Within the order of primates, humans are further classified into the superfamily Hominoidea. Species belonging to this superfamily are called hominoids (or apes)
Broader rib cage
and pelvis, helping
hominoids sit
upright by creating
a wide, stable chest
Lack of tail,
contributing to the
hominoid’s ability to
sit upright
Shorter spine
between the rib
cage and pelvis,
helping hominoids
sit upright
Increased cranium size as hominoid brains tend to
be larger and more complex than other primates
Typically longer arms
than legs (except Homo
sapiens), shoulder blades
that sit further back, and
shoulder joints that allow
the arm to swing back
Homo neanderthalensis
Lived in Europe/West Africa from 200 000 to 27 000 years ago. Short (males around
165 cm) and powerful, with
large brow ridges and brains slightly bigger than modern humans. They were expert toolmakers and hunters who were thought to have bred
with modern humans.
Primates
3D colour vision and
forward-facing binocular eye
A large cranium relative
to body weight
A large number of
sensitive touch receptors
in their fingertips
Prehensile hands and
feet consisting of five
digits each, with one
opposable digit to help
them grasp objects with
power and precision
Homo habilis
Living between 2.3-1.6 mya
in East/South Africa, members of H. habilis had 50% larger brains than the australopithecines, as well as smaller teeth and a less protruding face. H. habilis was similar to the australopithecines in that it
still had long arms and shorter legs suitable for climbing
homonins
bipedalism
Pelvis – Human pelvises are more shallow and bowl-shaped than other primates, whose pelvises tend to be vertically long and narrow.
The bowl-shaped pelvis helps provide support for the upper body whilst standing and walking upright.
– The human foot no longer has prehensile capabilities, and the big toe is in line with the other toes. Human feet also have two
arches and a wide heel, making bipedalism more energy e cient and less impactful on the foot.
The rib cage in humans is more barrel-shaped than gorillas who have funnel-shaped rib cages instead. This helps humans
to maintain an upright posture for a lengthy period of time.
Homo erectus
Appeared 1.8 mya in Africa, and
was later found throughout much
of Asia and Europe. Lived until as little as 200-300 000 years ago, and were much more human-like than anything prior – bigger brain, longer legs, shorter arms
and more sophisticated tools. Homo erectus are often credited with much of the migration
out of Africa.
evidence that homosapiens and homo Neanderthals
interbred
Nuclear DNA studies in 2010 show around 1–4%
of the human genome is identical to DNA found
in Neanderthals . This 1–4% similarity was only found in the genomes of non-African populations and not in sub-Saharan African genomes.
100 000 year old DNA from Neanderthal fossils
found in Siberia in 2016 contained a significant
amount of ancient human DNA not found in other
Neanderthal populations
Homo denisova
In 2010, scientists reported the discovery of bone fragments of a new hominin species
in Denisova Cave in Siberia. The bones were dated to around 40 000 years ago. Upon
analysis, nuclear DNA from the bone was found to be very closely related to Neanderthals,
but different enough to be a new distinct species, termed Homo denisova, or Denisovans.
Due to a lack of discovered fossil evidence, most of the inferences about the Denisovans have been made purely from DNA evidence. For example, only a few small teeth were
uncovered in the original Denisova Cave (Figure 6), as well as a partial jawbone discovered in the Tibetan Plateau in 2019.
Evidence for the ‘Out of Africa’ model
of early human migration includes:
greater genetic diversity in
African populations
* mtDNA traced back to common
ancestor in Africa
* existing fossil record, especially along
the east coast of Africa and into the
Middle East
* cultural artefacts, such as stone tools
and cave paintings
