life science exam Flashcards
cell theory
- all cells come from pre-existing cells
- cells are the basic unit of life
- all organisms are composed of one or more cells
prokaryote only
- no nucleus
- plasmids
- no membrane-bound organells
eukaryote only
- has a nucleus
- - contains membrane-bound organells
both prokaryote and eukaryote
- contain DNA
- contain ribosomes
- cytoplasm
- cell membrane
cell wall
protects the cell –> plant only
large vacuole
stores water, nutrients, and waste –> plant only
chloroplast
site of photosynthesis –> plant only
nucleus
controls cell activity and contains DNA
smooth ER
produces lipids
rough ER
transports proteins, protein synthesis
ribosomes
protein synthesis
mitochondria
produces ATP, cellular respiration (the squiggly one)
golgi apparatus
stores, modifies, and transports protiens
cell membrane
allows for certain substances to enter and exit the cell
cytoplasm
provides structure and holds organelles in place
lysosome
digests and recycles waste –> plant only
DNA
deoxyribonucleic acid: chemical component found in the nucleus that stores coded instructions. Has the code for different proteins and cells
structure of DNA
DNA is a double helix and is said to be anti-parallel. Held together by hydrogen bonds between base pairs
nucleotides
the basic structure of DNA
- deoxyribose sugar (the pentagon)
- phosphate (the small circle, LINK phosphate cycle)
- nitrogenous bases (rectangle)
chromosome
a thread like strand of DNA that is encoded with genes. humans have 46 chromosomes in each cell (23 pairs)
homologous chromosomes
similar in length, centromere position, banding pattern. one is inherited from mother, and one from father
karyotype
a picture of homologous chromosomes arranged from largest to smallest
down syndrome
three chromosomes at number 21
turners syndrome
only one sex chromosome
kleinfelters syndrome
three sex chromosomes
gene
a section of DNA containing instructions and codes which produce specific proteins
RNA
ribonucleic acid
characteristics of RNA
- single stranded
- contains uracil (U)
- ribose sugar
characteristics of DNA
- double-stranded
- contains thymine (T)
- deoxyribose sugar
transcription
occurs in the nucleus
- DNA unwinds to expose bases
- Free mRNA strands bind following complimentary base pairing rules
- mRNA strand is produced
translation
occurs in the cytoplasm
- mRNA attaches to a ribosome in the cytoplasm
- tRNA brings specific amino acids to the ribosome
- amino acids are joined together via a peptide bond and a protein is formed.
importance of the cell cycle
important for growth, repair, development, maintenance of cells
mitosis
1 cell division, 2 daughter cells, one parent cell, 46 chromosomes, diploid, somatic (body) cell, genetically identical
meiosis
2 cell divisions, 1 parent cell, 4 daughter cells, 23 chromosomes, haploid, gamete, genetically different
genotype
genetic makeup of an individual
phenotype
physical expression of a geneotype within an environment
apoptosis
programmed cell death
interphase
DNA replicates, chromosomes are not visible, longest stage of the cell cycle
prophase
chromosomes condense, spindle fibres form, nuclear membrane breaks down
metaphase
chromosomes line up along the midline of the cell
anaphase
sister chromatids separate to opposite ends of the cell
telophase
new nuclear membrane forms, spindle fibres disappear, chromosomes decondense
cytokinesis
division of cytoplasm into 2 genetically identical daughter cells.
allele
different versions of the same gene
homozygous
two of the same alleles of a gene eg bb or BB
heterozygous
two different alleles of the same gene eg. Bb
dominant
trait will always be expressed
recessive
traits will only be expressed if there is two
codominance
when two alleles are equally expressed
sex linked genes
carried on the X and Y chromosomes. Most traits are on the X chromosome as it is much larger.
steps to looking at a pedigree
- is the trait dominant or recessive?
– do all affected individuals have at least one affected parent
yes = dominant
no = recessive - is the trait sex-linked or recessive?
– DOMINANT: do all affected males have affected mothers and all affected daughters?
—- yes = X linked dominant
—- no = autosomal dominant
– RECESSIVE: do all affected females have affected fathers and all affected sons?
—- yes = x linked recessive
—- no = autosomal recessive
OR: autosomal = number of males and females affected is similar
X linked dominant = greater number of females effected
X linked recessive = greater number of males affected.
mutation
changes that occur at the DNA level that are inheritable. Caused by chance, cell division error, or from a mutagen
mutagen
chemical or physical agents that can cause a mutation to DNA
gametic mutation
occurs in testes and ovaries. it is inherited and can be passed to offspring
somatic mutation
occur in body cells. they are not inherited but may affect the person during their lifetime
gene mutations
occur when nitrogenous base is inserted, deleted, or rearranged
point mutation
one base is substituted for another. codes for the wrong amino acid resulting in a faulty protein
frameshift mutation
a base has been inserted or deleted. results in a non-functional protein
chromosomal mutations
occur due to non-disjunction –> when chromosomes don’t separate correctly during meiosis.
natural selection
selects for adaptations that allow for an organism to survive and reproduce
natural selection steps
- there is variation among species
- not all of the population survived (who did)
- those that survived reproduced
- overtime genes are passed to offspring
selection pressures
predators, food source, climate
gene pool
all of the different genes in a population
variation
within a species, there is variation in the gene pool. Individuals have the same number of genes but different alleles. variation (new alleles) arise from mutations
speciation
the process of forming a new species
steps in speciation
- species are isolated
- populations face different selection pressures and have adapted through natural selection
- become reproductively isolated from each other and are considered separate species
allopatric speciation
populations become geographically isolated and each population faces different natural selection pressures
geographical isolation
a geographical barrier that stops gene flow between isolated populations
temporal isolation
species mate at different times
behavioural isolation
animals have different mating behaviours
mechanical isolation
animals have different sized body parts = no gene flow = no babies
divergent evolution
when two or more species sharing a common ancestor become less alike overtime
homologous structures
structures evolved from a common ancestor but now perform different functions
convergent evolution
unrelated organisms independently evolve similarities when adapting to similar environments
analogous structures
animal structures that perform similar functions but arent closely related
artificial selection
selects adaptations or traits for the benefit of humans
fossils
remains / traces of an organism embedded into the earth. for a fossil to be formed, it must first be buried before it decomposes. bones are the most common thing found in fossils as they take the longest to decompose
transitional fossil
shows the intermediate state between ancestral form and that of the decendents
comparing DNA
organisms closely related have a higher percentage of DNA / genes in common
Comparing proteins
comparing the sequence of amino acids in a protein. can show the evolutionary relationship between species.
comparing embryology
study of the development in the structure and function of embryos
comparative anatomy
comparing physical structures found in organisms
vestigial structures
functionless structures found in organisms eg. wisdom teeth
biogeography
the study of how continents move and the impact on the location of organisms
lithosphere
describes the rocks, minerals, and molten magma found on earth
hydrosphere
all water on earth
atmosphere
the layer of gases surrounding the earth.
biosphere
composed of all organisms on the planet
oxygen cycle
oxygen is essential for life. It is produced by photosynthesis and is a reactant in cellular respiration –> used to create ATP.
photolysis
UV light splits water into hydrogen and oxygen (in the atmosphere
nitrogen cycle
a part of RNA, DNA and proteins.
nitrogen fixation
some bacteria convert nitrogen into nitrates or nitrites which is a usable form of nitrogen. Lightning can also fix.
phosphorus cycle
important for DNA, RNA, ATP.
eutrophication
dishwashing detergent and soil from farms contain phosphorus. run off from drains and farmlands increase the level of phosphorus within waterways. Increased phosphorus causes algal blooms, which block sunlight and halt photosynthesis. It also increases the levels of bacteria that take all of the oxygen from marine animals.
water cycle
essential for photosynthesis and cellular respiration and all living things need water. water cycles between the four spheres
transpiration
water is transferred from below the ground to the air by plants
carbon cycle
keeps carbon levels naturally balanced. earth would become inhabitable without it. Removed by photosynthesis and released by cellular respiration, fossil fuels, decomposition etc.
carbon sinks
where carbon is stored away from the atmosphere
eg. forests, oceans, rocks, organic matter in soil
the greenhouse effect
natural phenomena critical for life on earth. Some solar energy from the sun is trapped by gasses in the atmosphere and some is radiated into space = ideal temperature on earth.
greenhouse gases
help to retain heat on the earth
enhanced greenhouse effect
increased level of global warming caused by the increase of greenhouse gases in the atmosphere, trapping more heat energy
pollution
the addition of a substance into an environment by human activity, at a rate greater than can be rendered harmless by the environment and the organisms that live in it
contamination
where an external mixture gets mixed with the original matter. may be chemical, biological, or radioactive in nature. may or may not be harmful to the environment.
pollution vs contamination
pollution is harmful, contamination is not. You can have a contaminated environment without it being polluted, but it cannot be polluted without being contaminated. pollutants can be either foreign substances or a component of the original substance that has exceeded the harmless level.
waste
a material, substance, or by-product eliminated or discarded as it is no longer useful or required.
air pollution
harmful compounds get mixed with the atmosphere leading to depletion of the ozone layer and respiratory problems
water pollution
discharge or spillage of waste into different bodies of water
soil pollution
pesticides get mixed with soil and lessens its fertility
light pollution
bright lights result in astronomical interference and over-illumination
noise pollution
harmful noise may result in auditory problems as well as psychological issues
point source
able to point directly to the source of pollution
– a factory releasing mercury into a river
non-point source
no single location is the point of origin
– runoff of stormwater containing fertiliser
coral bleaching
where coral dies as protists living inside them can no longer perform photosynthesis = loss of colour and the coral’s death. warmer conditions make the coral stressed and they release the protists living on them.
gel electrophoresis
- DNA is collected and isolated
- DNA is fragmented into short lengths
- DNA is inserted into the gel with a micropipette
- electric current is run through gel
- DNA moves toward the positive electrode
- smallest fragment moves furthest away from well
- DNA pattern is compared with other samples.
