Stage 1 Biology FINAL EXAM

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diploid and haploid cells

• somatic (body) cells are diploid (have full set of chromosomes - 22 autosmal pair and 1 pair sex cells)

• homologous chromosome - 2 chromosomes that form a pair

• sperm and ova (sex cells) are haploid - only one set of chromosomes from each homologuspair

• formed through meiosis and only contain ½ bc they fuse during fertilisation and chromosome number doubles

transcription

• dna is in nucleus, ribsomes in cytoplasm, dna is too big to leave it

• gene is copied by RNA polymerase into messenger RNA (mRNA) to deliver from nucleus to ribsome

• mRNA produced through trasncription is copy of gene with the sequence of nucleotides for order og amino acids

1. RNA polymerase protein binds to DNA near gene coding for required protein

2. RNA polymerase unwinds double helix, exposing nucleotide base sequence of gene

3. RNA polymerase moves across exposed gene to synthesise mRNA molecule - working copy of gene taht can travel out of nucleus to be translated

translation

• amino acids are carried to ribosmoe during translation by tRNA (transfer RNA)

• tRNA molecule can only carry one specific amino acid, only bond to 3 specific base section of mRNA its complementary to

• ribsome moves acorss mRNA strand, tRNA carry specific amino acids into correct position in chain of amino acids

• ribosome facillitates formation of strong peptide bonds between them and make polypeptide chain

• polypeptide chain folds in precise way to make protein

• shape of protein is based on order of amino acids, shape determines function

1. mRNA is trasported out of nucleus to ribsomes in cytoplasm

2. ribsomeomes move along mRNA strand and assemble amino acids in sepcific order with help of tRNA molecules fomring polypeptide

3. polypetide folds into precise 3D shape forming funcitonal protein

cell differentiation 

• zygote divides many times by mitosis and makes genticially identical embyonic stem cells (ball of it)

• only some specific genes are switched on and produce specific proteins - gene expression - determines structure and function of specialisedd cells 

gene expression controlled - transcription factors

Transcription factors

• proteins that affect binding of RNA polymerase to particular gene on DNA

• each gene has short section of DNA called promoter region - located just before gene of DNA molecule

• if RNA polymerase cna bind to promoter region of gene its swtiched on, transcription happens

• if RNA polymerase cant find to genes promoter region its switched off

• repressors can bind to promoter region and block RNA polymerase from transcribing gene

gene expression controlled - epigentic tags (how each affects gene expression)

• epigenome - chemical tags DNA accumulates, additional level of coding on top of DNA base sequence

• do not affect DNA base sequence but change how cells read DNA and express it

• methylation of cytosine bases and acetylation of histones

osteoporosis description, lifestyle contribution (risk and development)

DESCRIPTION - bones are weak and fragile due to reduced bone density. resul in curvature of spine, increased risk of fractures/breakages

DEVELOPMENT - sedentary lifetyle leads to poor bone density (weight bearing excericse neeeded for developemtn and maintenence of bones). low in calcium and vitamin D is bad, vitamin D needed to absorb calcium, needed for bone formatoin. lack of exposure to sun lowers vitamin D

REDUCE - regular weight bearing excercise, outside excercise allows body to synthesise vitamin D in sun. diet w dairy and dark leafy greens high in calcium

atherosclerosis description, lifestyle contribution (risk and development)

DESCRIPTION - build up of fatty deposits in arteries, fomring plaques. thickens arter walls, narrows channel reducing blod flow and ability to deliver nutrients to organ systems. full blockage results in heart attack or stroke

DEVELOPMENT - high saturated and trans fats diet increases cholestrol increasing risk of fatty deposits building up. low in fibre increases risk as fibre helps lower cholestrol

REDUCE - excercise increases production of good cholestrol levels, lowers bad ones in blood,decreases risk. reduces blood pressure. balanced diet high in plant based food, fatty fish (omega 3) and low in saturated trans fats

hypertension description, lifestyle contribution (risk and development)

DESCRIPTION - pressure in blood vessels is too high, can stiffen and injure walls of arteries, accelerating atherosclerosis. untreated leads to heart failiure

DEVELOPMENT - high in sodium diet increases risk - kidneys cant excrete sodium efficiently enough, water is retained by body to dilute sodium in blood, increasing blood volume and pressure. chronic stress increases blood pressure due to release of stress hormones activating pathways to increase heart rate and blood pressure

REDUCE - regualr physical activity reduces blood pressure, makes heart stronger, reduces stress. low sodium and simple sugar diet leads to less water retentino therefore lowered blood pressure

Definition

type 2 diabetes description, lifestyle contribution (risk and development)

DESCRIPTION - hormonal system has reduced ability to control blood glucose levels due to increased insulin resistance, attributed to poor diet/lifestyle choices

DEVELOPMENT - pancreatic cells rpdoucing insulin are reduced due to inflammation (from diet high in saturated fats), overstimulatoin of pancreatic cells to produce insulin (high in sugar diet) over a long time period (tire and die off)

REDUCE - exercise is energy intesnive, lowers blood glucose levels, burns fats (weight loss) reduces risk, increases insuling sensitivity - balanced diet low in simple sugars and saturated fats reduces risk of insulin resistance developing

1. describe relationship between type 2 diabetes and average body mass

2. one limitation of investigation

3. how diet increases risk of developing type 2 diabetes

4. excercise level reduces risk of type 2 diabetes

1. From 1990 to 2000 the mean body mass of the population increased from 72.6 kg to 77.2kg. At the same time the percentage of the population with type 2 diabetes increased from 4.9% to 7.3%.

2. data is outdated (only up to 2000 not 2025), doesnt factor in cause of weight gain for all individuals within population

3. high in sugar overworks insulin producing pancreas, causes death of insulin producing cells in canreas, results in reduced ability to produce insulin in response to blood glucose

4. intense excecise leads to intense energy, lowers blood glucose levels burns fat, weight loss and reduced risk of t2 diabetes, increases insulin sensitivity

efficient exchange surface criteria 

• thin - reduces distance materials need to move during exchange

• moist - allow substances ot dissolve in water, assit in trasnport across exchange surface

• large total SA - provides more surface for exchange to happen

• rich blood supply - trasnport substances to and from exchange surfaces, maintains concentration gradeitn

ventilation

2 PROCESSES - INSPIRATION AND EXPIRATION

• air enters respiratory tract thru mouth or nose, passes through nasal cavity and is smelt, warmed, filtered, moistened. passes through pharynx, larynx, reaches bronchi. after gas exhchange, expanded lungs deflate, air forced back up repiratory tract to mouth/nose to be expelled

• movement of air is achieved by generating changes of pressure in chest cavity - intercostal muscles ribs and diaphragm involved

• in inhalation diaphragm contracts, flattens, intercostal muscles contract elevating ribcage up and out, making more space for lugns to expand into

• increases volume of chest cavity, lowers air pressure inside lugns compared to outside body

• in exhalation diaphragm relaxes and returns to resting dome shape and intercostal muscles relax, depressing ribs downwards and inwards

• decreases volume of chest cavity, increases air pressure inside lungs compared in the outside body, expelling air from the lungs

gas exchange in alveoli

• occurs between alveoli and capillaries

• capillaries have high co2 conc, low o2, air has high o2 low co2, causes o2 to diffuse from alveoli to capillaries down conc gradient (opposite direaction for co2)

facillitated by:
otal surface are of alveoli within lungs is extremely high because there are millions of alveoli

• outside surface of alveoli are covered with lots of capillaries

• distance of diffusion is very short because alveoli surface and capillary walls consist of single layer of epithelial tissue making them very thin

• exchange of gases across alveoli assisted by presence of film of moisture covering inside surface of them - allows gases to dissolve in moisture and diffuse across

plasma and blood vessels 

• fluid component of blood cells 

• includes nutrients from digestion needed for cells for energy and growth, hromones transported to cells, salts maintaining osmotic pressure important for muslc econtraction, CO2 - metabolc waste, urea metabolic waste, antibodies for disease 

arteries

• blood vessels that take blood away from heart - carry oxygenated blood EXCEPT FOR PULMONARY ARTERY carries deoxygenated blood away from heart into lungs

• blood in arteries transported through narrow central core under high pressure - big wall little lumen

• have thick layer of smooth muscle and elastic fibres to cope w pressure\branch into arterioles, smaller and lead to capillaries

• each heartbeat makes surge of blood enter arteries, expand to cope with increased blood flow

• expansion and recoil is pulse

• contraction and relaxation of smooth muscles within arteries is controlled by central nercous system - allows body to adjust flow of blood within body when needed

veins

• venules (very small veins) extend form capillary beds, intersect to form veins

• blood vessels that take blood back into heart - carry deoxygenated blood EXCEPT FOR PULMONARY VEIN carries oxygenated blood back into heart from lungs

• conssit of thin layer of smooth muscle and elastic fibres

• wide central tube - only blood vessel with valves - open in one direction to prevent backflow of blood

• blood pressure in veins is lower than arteris and flow of blood is flower - greater distance from heart and wide central tubes

• movement of blood can be facillitated by contractinos of adjacent skeletal muscles

• muscles contracting and expanding supplies pressure on adjacent veins, adding pressure for blood flow througb one directional valves and back towards right of heart

capillaries

• onnect arteries with veins (arterioles w venules)

• only blood vessels where substances can be exhanged between blood and bodys cells

• consist of single layer of epithelial cells, cnetral core is very narrow, ensureing red blood cells flow through in single file so theres less distance for gas exchange between red blood cells adn body cells

• oxygenated blood enteres containing high O2 and useful substance conentration, low CO2 - useful is diffused with concentration gradients across capillary wall into surrounding tissue fluid

• waste products diffuse with concentration gradients form body cells and tissue fluids into blood

• blood leaving capillaries is deoxygenated blood

human circulatory system

• 4 chambered heart and double circulations - pulmonary and systemic

• right side of heart pumps deoxygenated blood to lungs, blood is oxygenated and returned to left of heart - pulmonary ciculatoin

• left side pumps oxygenated blood to rest of body to supply cells with oxygen and nutrients. blood becomes deoxygenated in process, metabolic wate diffuses into it

• deoxygenated blood is moved back to right of heart, completeing systemic ciruclation

• double circulation - blood travels through ehart 2 times to comeplte one full circulation of body

• blood travelling thru lungs looses lots of blood pressure along capillaires, speed it travels slows

• blood travels back to left side of heart so oxygenated blood can be pumped at high pressure so body cells receive blood supply quickly and frequently
  
  
  main advantage of a double circulatory system is the efficient and complete separation of oxygenated and deoxygenated blood, which allows for higher blood pressure in the systemic circulation (to the body). This higher pressure leads to more efficient and faster delivery of oxygen and nutrients to the body's tissues and organs, supporting the high metabolic needs of active animals like mammals. 

human heart (pulmonary and systemic circulation, structure)

• located in thorax between lungs

• cardiac muscle suplied with oxy blood by coronary arteries, deoxy leave by coronary veins

• divided into 4 chambers - L and R seperated by septum

• blood enters heart via atria (upper), pumped out by muscly walls of ventricles (lower)

• L ventricle thicker because it pumps blood at higher pressure

• R ventrickle thinner ebcause pumps deoxygenated shorter distance

• 4 valves prevent backflow

• atrioventricular between atria and ventribles,

• semilunar seperatibng RV from pulmonary artery, other from LV and aorta

• connected to inner walls of heart by tendons

cardiac cycle

• heart relaced - blood flows to atria

• atriac contract, force blood to ventricles

• ventricles contract - blood pressure inside rises, increased pressure closes atrioventricular valves (LUBB sound, prevent backflow)

• rising pressure pushes open semilunar valve openm blood slows into arteries

• finished contractoin makes pressure fall, semilunar close (DUBB SOUNDS)

movement of blood thru heart

deoxygenated blood from around the body enter the right ventricle via the superior and inferior vena cava. atria contracts, pushing blood into the ventricle, and the tricuspid valve opens and closes (due to teh rising pressure) so backflow is prevented. right ventricule contracts and pushes blood through semilunar valve into the pulmonary artery (failling pressure closes semilunar valve and prevents backflow). pulmonary artery runs blood towards the lungs, where gas exchange occurs, once it is oxygenated, blood runs back to left atrium via the pulmonary vein and is pumped to the left ventricle (opening and closing of bicuspid valve), pumped again thru the aorta/aortic valve and around through tehe body



cardiac muscle of heart is supplied w oxyblood by coronary arteries adn leave by coronary veing

digestive system organs explanation and diagram

what happens in mouth(perstalsis define as well)

• ingested - digestiion begins

• food mechanically broken down by teech (mastication) - mixes food with saliva from salivary glands

• lubricates food, increases SA for salivary amylase to cehm digest complex carb starch into polysacharides and maltose

• swalled thru pharyx to oesophagus, epglottis extends and covers widnpipe to stop chocking

• peristalsis (wave of sequential smooth muscle contractions) pushes food down oesphagus

absorption and small intestine

• small intestine - hollow tubelike, smooth muscle and perstalsis that propels food through small intestine, duodenum, jejenum, ileum

• inner lining covered with villi that absrob digested nutreints

• increase SA of small intestine

• most occurs at jejenum

• single latered epitehlial lining reduces distance for nutrients, is moist

• simple sugars and amino acids absorbed across epithelial lining to blood capillaries of villi, fatty acids and glycerol absrobed into lacteal

lacteal

• lymph capillary pary of lymphatic system

• simple sugars and amino acids absorbed across epithelial lining to blood capillaries of villi, fatty acids and glycerol absrobed into lacteal

• nutreints are prcessed by liver, avaialbel for budy to use 

macromolecule, site of chem digestion, products, how transported

chem digestion of carbs, proteins, fats (image)

colon and egestion

• undigested materials (distery fibre, water, dissolved salts, older cells) reach colon

• absrobs water and dssolved salts, trasports stool through peristaltic movements into rectum to prepare for elimination

• intestinal bacteria ferments dietary fibre in large intestine and prodcues short chain fatty acids, vitamin k, water, gasses

• people cant digest fibre bc they dont have necessary enxymes

• indigestale stuff is faeces - stored in rectum exprelled via anus

nephron and structure

• structural and functional unit of kidney

• over a million in each, large SA for filtration and selective reabsorption

• has bowmans capsule, glomerulus, renal rubule

• glomerulu - cluster of capillaries located in bowmans capsule

• renal tubule 3 parts - proximal, loop of henle, distal

• end of tubule joins to collectivng duct, connected to ureter

filtratoin

• blood transported from renal artery w high pressure to glomeruls, filered here

• high blood pressure causes wataer and small substances to pass thru capillary walls, enters blwmans capsule

• larger components arent filtered

• liquid passing to bc is glomerular giltrate

selective reabsorption

• filtrate in bowmans capsule flows into tubule, useful stuff are reabsorbed, occurs across length of tubule and some are thru collecting duc (e.g. water)

• Proximal tubule: 100% of glucose and amino acids reabsorbed; large amount of water and salts also reabsorbed.

• Water reabsorption: About 99% of filtered water reabsorbed by osmosis across tubule and collecting duct (varies with diet, medications, environment).

• Salt reabsorption: Amount reabsorbed varies depending on individual factors.

• Urea reabsorption: ~50% reabsorbed passively along tubule; collecting duct can reabsorb more if needed.

• Urine contents: Remaining urea, nitrogenous wastes, excess water, and other unabsorbed substances exit via collecting duct → bladder.

• Blood return: Reabsorbed substances returned to circulation via renal vein → heart.

explain selective reabsorption for the nephron diagram

structure and function of parts of nephron

guard cell - plant tissue sstem, image, and description of structure and function

• dermal tissue system

• pair of bean-shaped cellsm surround stoma

• open and close to allow diffusion of gasses

• thick cell walls facing stoma, thin facing adjacent epiderman cells

• open when gain water and become turgid

• thin outer walls bend more easy, causing themt o curve and open stoma

root hair cells - plant tissue sstem, image, and description of structure and function

• dermal tissue system

• single-celled extensions of epiderman cells in root

• increase SA of cells

• increase SA increases efficinecy at absorbing water and mineral salts form soil- plant tissue sstem, image, and description of structure and function

xylem - plant tissue sstem, image, and description of structure and function

• vascular tissue system

• very long hollow tubes consisting of dead cells

• arranged end to end, have no cell walls between cells, form continouos tube that water can move through

• tough walls, contian woody material (ligning) that thickens vessels

• thick walls are impermeable to water so cant leak

• lignin deposited in spiral-shape to allow it to remain flexible 

palisade mesophyll - plant tissue system, image, and description of structure and function

• ground tissue system

• reside directly under upper epidermis, stakcer vertically to max space and fit more in 

• receive most light, contain most cholorplast to max absorption of light and of photosynthesis 

structure and function of leaf

• attatched to the stem by a petiole, continues into most ribs to form mid rib

• The surface is called lamina

• 2 main functions - gas exchange and photosynthesis

• broad, flat lamina, increases SA

• thin to increase the efficinety of gas exchange

• stomata facillitate gas exchange

• cells have cholroplasts for photosynthesis

• spiralling arrangement of leaves ensures each leaf is exposed to sunlight

waxy cuticle, upper epidermis, lamina, palsiade mesophyll, spongy mesophyl, vascular bundles, lower epidermis descriptions and functions

xylem

• extend from roots, through to stem, up and through leaves

• unidirectional passive transport of water and mineral nutrients from roots to other plant parts

• transpiration stream - continuous upward flow of water in xylem vessels

• long, hollow tubes, fused dead cells with no contents

• arranged end to end, no cell walls bteween (continous tube water can flow thru)

• tough walls made of liging - thickens vessels, helps withstand pressure 

• lignin deposited in spiral shape to allow flexibility 

phloem

• transport organic molecules (sucrose, amino acids) synthesised by plant

• transported to growing parts of plant and to storage organs (e.g. tubers) through translocation

• flow of molecules in phloem is bidirectional (up and down tubes)

• consist of living cells, don’t have nuclei, contain porous sieve plates at either end so cytoplasm is connected and molecules can move thru them

• transport requires energy - sieve tube attached to one or more companion cells that provide the energy

define interspecific and intraspecific interactions and name three type of interspecific interactions

intraspecific - interactions between same speices

interspecific - interactions between different species

types:

1. competition

2. predation

3. symbiosis

competition

• ompete for same resources (e.g. light, oxygen, nutrients, prey, space, sexual partners)

• no 2 species have identical requirements - overlap is where there is competition

• outcome generally has negative effects on weaker competitors

• more intense amongst members of smae species 

• outcompeted species must adapt to remaining available resources or become extinct 

• significant drive of natural selection and evolution

predation

• one organism (predator kills and consumes another or parts of it (prey)

• generally occurs between different species, when same sepcies it is cannibalism

• cannibalism helps species survive times of limited resources

• affects no. of organisms in population, biodiversity of community, evolution of organisms involved

herbivory

• consumption of all or part of photosyntehtic organism, generally plant, by animal

• can result in death of photosyntehtic organisms but nto always

• photosynthetic organisms are producers in most food chains

• herbivores and plants drive adaptations in both species

• herbivores - digest and extract nutrients from plant matter plants - physical and chem defences

symbiosis

• distinct relationships between organisms of 2 diff species

• 3 types - mutualism, commensalism, parasitism

mutualism 

• both species benefit

• e.g. on image

commensalism

• one species benefits, other in unaffected

• e.g. on image

parasitism

• one benefits, other is harmed

• invovles organisms called parasite harming organism called host

• e.g. on image 

autotrophs (and producer define)

• convert inorganic maetrials into organic molecules needed to sustain life

• carry out photosynthesis - light energy convereted to chemical energy

• some do chemosynthesis (organic compounds from chemicals)

• producers - organisms that carry out autrtophic nutrition 

heterotrophs

• organimss that feed on other organisms to obtain organic molecules

• invovles eating organimc material of other organisms and digesting it

• if only feed on producers - herbivore

• if only feed on other animals - carnivore

• omnivore - both

decomposers

heterotrophs that extract energy from remains/waste products of organisms from all trophic levels - break down dead matter and recycle nutrients - wihtout, dead organisms and matter build up

food chains and food webs

• show feeding relationships

• arrows point in direction energy and nutrients mvoe

• many consumers represented at several trophic levels, therefore food web is more realistic representation

• decomposers breakdown at every level

trophic levels, consumers

trophic level - relative position of an organism in the food chains

1st - producer, synthesises own energy-rich compounds (e.g. plants)

remaining - heterotrophs, feed on producers and other animals consuming producers, consumers

first consumer in fodo chain - primary consumer - 2nd trophic level

seconadry consumer - eats primary consumer, 3rd trophic level

consumer at top of food chain - apex predator, no natural predators

food web - many linked fodo chains, more accurate

biodiversity (+define genetic, species, and ecosystem diversity - answer on image)

• variety of living things on earth

• generally expressed at 3 different levels - genetic, species, and ecosysten diversity

importance of biodiversity

• maintain contunity of life on earth 

• privision of o2, food, water

• provision of resources and raw materials

• source of organic moelceus for medicinal purposes

• breakdown of waste materials

• provision of natural sites for recreation and appreciation of nature 

dichtomous key

• presents a series of mutually exclusive choices, one applies to a species, lead on until the correct statement leads to the identification of the species

reproductive isolation (possibly add more to this)

• seperate species cannot interbreed and preduce fertile offspring - species are reprodcutively isoalted from other ones

• attraction of mates - pheramone chemicals released by one of the sexes - only attract members of their own species

• reproductive barriers foring isolating boudnaries around closely reltaed speices can be divided into two groups - prezygotic and postzygotic isolating mechanisms 

pre-zygotic and post-zygotic mechanisms

PRE ZYGOTIC

• any mechanism occuring before gametes fuse to make zygote

• e.g. diff matinc calls and rituals, specific pheramones, difference in flower shape/genitalia, different seasons/times for reproduction, inability of sperm to survive female reproductive system

• pollen tubes unable to grow in ovules in a flower

Post Zygotic

• any mechanism after gametes fuse to form a zygote

• e.g. zygote fails to develop (miscarraige), young fails to reach sexual maturity, offspring live but are infertile