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