C&C Ch. 3 Flashcards
similarities between even widely disparate types of organisms exist at
every level, from familiar, externally visible resemblances, to profound resemblances in life-cycles and the structure of the genetic material
what is the explanation for the similarities between different groups of organisms?
organisms are related through an evolutionary process of descent from common ancestors
list the various similarities between species
- biological classification
- embryonic development
- vestigial organs
- sexual reproduction
- inheritance
- genes
- mutations
- DNA sequencing
similarities between mammals and other vertebrates
basic features of their skeletons, and their digestive, circulatory, and nervous systems
similarities between mammals and insects
segmented body plans, their common need for sleep, the control of their daily rhythms of sleep and waking, and fundamental similarities in how the nerves work
systems of biological classification have long been based on
easily visible structural characteristics
describe the different levels of biological classification
domain
kingdom
phylum
class
order
family
genus
species
brief description of arthropods
phylum which includes insects, among which flies form one group (all have only one pair of wings) as well as butterflies and moths (whose members all have fine scales on their two pairs of wings)
similar species are grouped into the same
genus
what do organisms in a genus have in common?
they are united by a set of characters not shared with other genera
naming system used by biologists
genus name followed by name of the species
as you go down the hierarchy of the groups, the groups
share more and more traits that are lacking in other groups
how can we discern an inferred pattern of genealogical relationships between groups of organisms?
by directly studying the information in their genetic material
give 2 examples of instances where there are modifications of the same structure in different species
- the bones of bats’ and birds’ wings indicate that they are modified forelimbs
- the internal structure of the flippers of whales is like the feet of other mammals except for an increased number of digits
evidence that whales are modified mammals
they breath with lungs, not gills, and suckle their young
according to fossil evidence, what did the two mares of limbs of land vertebrates derive from?
the two pair of fins of the lobe-finned fishes; the earliest land vertebrate fossils had more than five digits on their limbs (like fishes and whales)
give an example of a known case in which the same basic structure was considerably modified during the course of evolution by the demands imposed by different functions
- three small bones in mammals’ ears, which transmit sound from the outside to the organ that transforms sound into nerve signals
- develop from rudiments in embryonic jaw + scull, and in reptiles enlarge during development to make parts of the head and jaw skeleton
- fossil intermediates that connect reptiles with mammals show successive modifications of these bones in the adults, finally evolving into the ear bones
how does embryonic development provide examples of similarities between different groups of organisms?
embryonic forms of different species are often extremely similar, even when the adults are very different
give an example of a similarity in embryonic development between mammals and fish
at one stage in mammalian development, structures appear that resemble the developing gill slits of fish embryos - developing blood vessels require the presence of gill slit rudiments to guide them to form in the correct places
what are vestigial organs?
organs, tissues or cells in a body which are no more functional the way they were in their ancestral form of the trait
why are vestigial organs interesting?
such cases tell us that evolution does not always create and improve structures, but sometimes reduces them
example of vestigial organs in humans
- appendix
- a greatly reduced version of a part of the digestive tract that is quite large in orangutans
compare primitive snakes with present-day snakes
- fossils of primitive snakes have been found with almost complete hindlimb, indicating that snakes evolved from lizard-like ancestors with legs
- body of a present-day snake consists of an elongated thorax, with a large number of vertebrae
example of vestigial limbs in legless animals
in the python, the change from the body to tail is marked by vertebrae with no ribs, and at this point rudimentary hindlimbs are found:
- pelvic girdle, pair of truncated thigh bones
- their development follows the normal course for other vertebrates, with expression of the same genes that normally control limb dev.
- a graft of python hindlimb tissue can even promote the formation of an extra digit in chick wings
what is a basic feature of all animal, plant, and fungal life?
their tissues are made up of essentially similar units, ce;;s
cells are the basis of the bodies of all organisms other than
viruses
define a eukaryote
all cellular non-bacterial life
how are cells organised in eukaryotes?
into the cytoplasm and the nucleus within it that contain the genetic material.
describe the cytoplasm of a cell
contains a complex set of sub cellular structures (organelles)
two of the most important organelles
mitochondria that generate cells’ energy, and chloroplasts in which photosynthesis in a green plants’ cells occurs
what did chloroplasts and mitochondria descend from?
bacteria that colonised cells and became integrated into them as essential components
how are bacteria both similar and dissimilar to eukaryotes?
they are also cells, but simpler ones with no nucleus or organelles
bacteria and similar organisms are called
prokaryotes
describe the only non-cellular forms of life
viruses parasites that reproduce inside the cells of other organisms, and consist simply of a protein coat surrounding their genetic material
what do most of the structures in cells consist of and why are they useful?
proteins:
- enzymes
- storage or transport functions
- structural proteins
- communicating information
enzyme
take a chemical and carry out a procedure on it, eg snipping a chemical compound into two components
example of storage or transport functions of proteins
- haemoglobin in RBCs carries oxygen
- ferritin binds and stores iron in the liver
example of a structural protein
keratin that forms skin, hair, and fingernails
examples of proteins that communicate information
- hormones circulate in the blood and control many bodily functions
- proteins located on cell surfaces are involved in communication with other cells (eg signalling to control cell behaviour during development, communication between eggs and sperm in fertilisation, and parasite recognition by immune system)
how is myosin used in different organisms?
motor protein involved in signalling in the flies’ eyes and in the ears of humans (one form of deafness is caused by mutations in the gene for this protein)
why does the international numbering system of enzymes categorise enzymes by the job they perform and not the organism they come from?
so many enzymes are found in cells of a very wide range of organisms
describe the metabolic pathway that is same for many organisms
- there is an energy source
- cell takes the initial compound through a series of chemical steps, some of which release energy
- each sub process is carried out by its own enzyme
similarities between respiration in lizards and humans
when lizards tire after running, this is caused by the buildup of the chemical lactic acid, just as in our muscles.
the metabolic pathway by which the skin pigment melanin is made is the same in
ourselves, other mammals, butterflies with black wing pigments, and even fungi. many of the enzymes involved in this pathway are also used by plants to make lignin (main constituent of wood)
function of inhibitors contained in cells
carry out control functions
define proteins
very large molecules made up of strings of dozens to a few hundreds of amino acid subunits
how many amino acids are used in the proteins of living organisms?
20
what is the complex 3D structure of a protein determined by?
the sequence of amino acids in its constituent chain or chains
what have studies of the 3d structures of the same protein across huge evolutionary distances, such as between bacteria and mammals, shown?
that these are extremely similar, even if the sequence of amino acids has changed greatly
why can sets of the same genes in the same order be found in the human genome and in the chromosomes of other mammals such as cats and dogs?
the order of genes on the chromosomes can be rearranged during evolution, but changes are infrequent
define a chromosome
a single very long DNA molecule encoding hundreds or thousands of genes
why do some mutations not change the protein sequence?
there are 64 possible triplets of DNA letters and only 20 amino acids used in proteins
to what extent does the genetic code differ across the entire range of living organisms?
only very slightly
compare and contrast protein synthesis in different cells
process is essentially the same in all cells, though in eukaryotes it occurs in the cytoplasm and the message must first move out of the nucleus to the translation machinery.
describe the importance of non-coding DNA
acts as sites for binding proteins that turn the production of the RNA messages of genes on or off
eukaryote cells undergo —— cell division processes
similar
how can single-celled organisms such as an amoeba or yeast reproduce?
simply by division into two daughter cells
describe and explain why plants and animals have different sets of signalling processes involved in development and differentiation?
- many signalling processes involved in development and differentiation of particular tissues, such as nerves, are found to be shared by all multicellular animals
- land plants use a different set because the fossil record shows that multicellular plants and animals have separate evolutionary origins
describe how cell division is controlled and why
- cells have enzymes that can distinguish new DNA from the old template DNA
- this allows errors in copying to be detected and corrected before division of the cell
describe the genetic material of many bacteria
have just one circular DNA molecule
describe the genetic material of some viruses, eg influenza and AIDS
- have genes made of RNA
- proof reading that occurs in DNA replication does not happen when RNA is copied, so the viruses have very high mutation rates and evolve rapidly within the host’s body
eukaryotes and prokaryotes differ greatly in their amounts of…
non-coding DNA; E.COLI has 86% protein-coding DNA. in contrast, less than 2% of the DNA in the human genome codes for protein sequences.
why is the number of proteins that a human can make probably much larger than the number estimated by genome sequencing?
very small genes, or unconventional ones, may be missed (eg genes that lie within other genes)
what is much of non-coding DNA made up of?
viruses and other parasitic entities that live in chromosomes
describe the similarities in the life-cycles of eukaryotes
many, though not all, eukaryotes have a sexual stage in each generation, in which the maternal and paternal genomes of the uniting egg and sperm combine to make an individual with 2n chromosomes
each egg or sperm has —– —— —– of an organisms’s genes; upon the union of egg and sperm at fertilisation, the cell will have —- —– —-
one complete set; a double set (one from mother and one from father)
how is it clear that the basic features pf sexual reproduction must have evolved long before the evolution of multicellular animals and plants?
- from the common features displayed in the reproduction of sexual unicellular and multicellular organisms
- the similar genes and proteins that have been discovered to be involved in the control of cell division and chromosome behaviour in groups as distant as yeast and mammals
describe how reproduction works in asexual species
mothers produce daughters without a reduction of chromosome number from 2n during egg production.
all multicellular asexual organisms show clear signs of being descended from…
sexual ancestors
what may happen if a mutation results in a change in the amino acid sequence of a protein?
the protein may malfunction. if it is an enzyme, this can cause the metabolic pathway to which it belongs to run slowly, or not at all.
what happens if mutations affect the control systems for cell division?
this can result in uncontrolled cell division and malignant growth of the cell lineage
what mechanism is in place to mitigate the impact of mutations in cell division control system genes?
it is unusual for both members of a pair of genes in a cell to be mutant, and one non-mutant member of the pair is often enough for correct cell functioning.
what is the link between harmful mutations and evolution?
- mutations that cause failure of an important enzyme or protein may lower the survival or fertility of affected individuals
- the gene sequence that leads to the non-functional enzyme will thus be under-represented in the next generation and will eventually be eliminated from the population
- a major role of natural selection is thus to keep the proteins of most individuals working wwell
when can mutations causing loss of function contribute to evolution?
when selection no longer acts to eliminate them (eg appendix)
describe the correlation between genome constitution and relation of species
- DNA sequences of a given gene will be most similar for more closely related species
- the amount of difference increases roughly proportionally to the amount of time separating two sequences being compared
- this property of molecular evolution allows us to estimate times of events that cannot be studied in fossils using a molecular clock
