biology unit 1 aos 2

✅cells to systems - organ systems

organ systems are groups of organs that perform a major function. some organs + tissues are involved in multiple organ systems.

✅cells to systems - levels of organisation

1. cells

2. tissues

3. organs

4. organ systems

5. organisms

✅cells to systems - 4 basic types of tissue

• muscle tissue - contract + produce movement

• nervous tissue - involved in communication

• epitheleil tissue - covers surfaces at interface of body + external environment (external includes anything that hasn’t passed a membrane yet, incl trachea, digestive tract, etc).

• connective tissue - connects other tissue (made of both extracellular matrix [not made of cells] and cells)

✅cells to systems - nervous tissue types

• sensory neurons - sense stimuli from body extremities + send messages to central nervous system (brain + spinal cord)

• interneurons - connect sensory + motor neurons in CNS → relay messages

• motor neurons - send messages from CNS to muscles or glands →

• glialcells - support + protect neurons

✅cells to systems - epithelial tissue examples

• epidermis - outer layer of skin

• mucuos membranes - ex. stomach lining, airways

• reproductive system

• exocrine glands - ex. sweat glands

✅cells to systems - muscle tissue types

• skeletal muscle - attatched to skeleton. striated. voluntary contracts.

• cardiac muscle - heart walls. striated. involuntary contracts.

• smooth muscle - surrounds organs. non-striated. involuntary contract.

✅cells to systems - connective tissue types

• loose connective tissue - areolar, adipose (fat), reticular

• dense connective tissue - regular (ex. tendons + ligaments), irregular (ex. dermis), elastic

• cartilage

• osseous tissue (bone)

• blood

✅cells to systems - organs

organs are structures made of a group of tissues (often all four tissue types) that perform a function.

✅✅digestive system

organ system that breaks down food + absorbs nutrients

✅✅digestive system - route + what is being digested

mouth - carbs

oesophagus - carbs

stomach - proteins

small intestine - carbs, fats, proteins

large intestine - undigested carbs

✅✅digestive system - alimentary canal

mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus

✅digestive system - accessory organs

liver, pancreas, gallbladder, salivary glands

✅✅digestive system - mouth

site of ingestion.

mechanical digestion - teeth break food into smaller pieces. saliva mixes with food = softer → easier form into bolus + easier to chew. tongue helps move food around.

chemical digestion - salivary ducts release saliva in mouth. its amylase enzymes start breakdown of carbs.

✅✅digestive system - processes in digestion

ingestion - taking in food

digestion - breakdown of big molecules, splitted into smaller ones either chemically or mechanically in order to increase SA:V ratio for absorption

absorption - takes in small molecules (after splitted in digestion) into bloodstream

egestion - removal of waste products as faeces

✅✅digestive system - oesophagus

hollow tube connecting mouth + stomach for food to move through by peristalsis. saliva is delivered here → slight breakdown of carbs + fats

d✅✅igestive system - peristalsis

wave like muscular contractions. that help food move along the digestive tract. also helps churning in stomach

✅✅digestive system - stomach

temporary storage for food. stomach lining is acidic so pepsin enzyme can chemically digests proteins. mucuos protects stomach from acidic lining. muscular movements (churning) mechanically digests food by mixing the juices and food together and breaking it into smaller pieces. churning also helps food move into small intestine as chyme.

✅✅digestive system - chyme

partially digested food

✅✅digestive system - small intestine

main site of nutrient digestion + absorption. chyme enters through duodernum and goes through jejenum and ileum.

• carbs - pancreatic amalase enzymes + enzymes on small intestine lining break down carbs. → absorbed as glucose through small intestine walls

  • some carbs are undigested and continue to large intestine

• proteins - pancreatic trypsin enzymes + small intestine lining enzymes break down proteins.

  → absorbed as amino acids through small intestine walls

• fats - bile from gallbladder + liver break down fats smaller (mechanical digestion). then pancreatic lipase enzyme breaks down fat.

  → absorbed once is smallest molecule through small intestine walls

• brush border enzymes = enzymes on small intestine lining that break down carbs + proteins

• small intestines lining absorbs smallest broken down molecules nutrients into bloodstream

• vili increase surface area for nutrient absorption

✅✅digestive system - large intestine + rectum + anus

small intestine delivers chyme to cecum (sack at start of large intestine). moves to colon where it directly absorbs water + vitamins + minerals into bloodstream through osmosis - not digestion. large intestine contains lots of bacteria + archaea that produce vitamins B and K and neutralise bile acids + other chemicals in chyme. as water is lost, chyme becomes more solid and compact → turns into faeces to be stored in rectum and egested out of anus.

✅✅digestive system - liver

liver produces bile (which starts breakdown of fats in small intestine). when eating, some bile goes directly to small intestine from liver and some goes to gallbladder. when not eating, all goes to gallbladder for storage.

also has many other functions - can store glucose as glycogen → regulates glucose levels + metabolism (storage + release of glucose when needed for energy), stores nutrients, removes toxins from blood (excretory system mentioned),

✅✅digestive system - gallbladder

gallbladder is under liver. liver’s bile is stored + further concentrated in the gallbladder. when eating, gallbladder releases bile into small intestine (duodenum)

✅✅digestive system - pancreas

• makes pancreatic juice which contains digestive enzymes.

• when food leaves stomach, pancreatic juice goes to small intestine to break down carbs + proteins and further break down fats.

• pancreatic juice also contains bicarbonate, which neutralises pH of chyme exiting the stomach

• the pancreas also regulates blood sugar levels (releases insulin + glycogen)

✅✅digestive system - chemical digestion

the breakdown of carbs, proteins and fats into smaller molecules using digestive enzymes + other chemicals

. enzymes need specific pH + other factors to work the best. stomach lining is very acidic and small intestine lining is slightly alkaline for example.

✅digestive system - mechanical digestion

physically breaking food into smaller pieces. examples - chewing in mouth + churning in stomach.

✅digestive system - salivary glands

produce saliva + release into mouth and oesophagus. contains enzymes which chemically digest food + lubricates food → easier to swallow

✅✅excretory system - functions + organs involved

• removes wastes from the blood via excretion + maintains water + ion balance

  • (sweating and breathing also remove waste from blood but most is excretion)

• urinary = kidneys, bladder (+ureters and urethra)

• other = lungs, liver, skin

✅✅endocrine system - functions + organs involved

• responsible for the production and secretion of hormones which are chemical messengers that control and regulate bodily processes to maintain homeostasis.

• hypothalamus, pituitary gland, thyroid gland, thymus, pancreas, adrenal glands

✅excretory system - kidneys

• main organ that seperates waste out of blood. they have millions of nephrons which filter blood.

• kidneys are also responsible for water and ion balance.

  • water balance alters blood pressure

  • ion balance alters pH of blood

• renal artery brings blood in to kidney

• renal vein take filtered blood away from kidney

• ureters take waste from blood away from kidney to bladder

• has regions - outer is cortex and inner is medulla

✅✅excretory system - nephrons

the glomerulus (capillary ball) filters out small particles in blood → tubules release needed nutrients back into the blood (including some water) and remove wastes which include nitrogenous waste, salts and some water. these wastes form urine.

• reabsorbed = from tubule to capillaries (wanted in blood)

• secreted = from capillaries to tubule (unwanted in blood, becomes filtrate)

• in blood, most ammonia has been converted to urea, but some ammonia is still in blood. some ammonia is filtered in bowmans capsule, but some isnt, so has to be secreted

1. renal arterioles + capillaries - renal artery branches out into arterioles which then branches out into capillaries which come to the glomerulus. capillaries then keep wrapping around the tubules, reabsorbing + secreting things.

2. glomerulus - ball of capillaries that sits in the bowman’s capsule

3. bowman’s capsule - filters blood by letting through small particles (includes water, urea, salts/ions, small toxins/drugs, glucose, amino acids. some urea, toxins + ions are too big or attatched to something too big to be filtered. also red blood cells are conveniantly too big). this becomes the filtrate that runs in the tubules

4. proximal convoluted tubule - the capillaries reabsorb glucose, amino acids, some water and some salts/ions through active transport. urea + toxins are secreted.

5. loop of henle - in descending limb, water is reabsorbed. in ascending limb, ions are reabsorbed

   • longer loop of henle = more water reabsorbed (camels need to reabsorb as much as they can)

6. distal convoluted tubule - reabsorbs water + salts/ions as needed. secretes salts/ions and toxins as needed. (fine-tuning)

7. collecting duct - reabsorbs water (in response to ADH) + salts/ions as needed. secretes salts/ions, toxins and urea as needed → filtrate is now urine + can leave kidney → ureters → bladder → urethra

✅✅excretory system - liver

• converts ammonia in blood into urea

  • when amino acids (from protein) are metabolised, toxic ammonia is produced

  • ammonia is sent to liver where it is broken down into urea which is safer to travel in the bloodstream. then travels to kidneys to excrete urea in urine

• detoxifies drugs + alchohol in blood

✅✅excretory system - skin

• removes excess water + salts through sweat

✅✅excretory system - lungs

• removes carbon dioxide from blood

✅✅excretory system - ureters

urine is released from the kidneys and these two tubes carry the urine to the bladder.

✅excretory system - different wastes + sources in body that have to be excreted somehow

• ammonia - from amino acid (protein) metabolism

• urea - from processing of ammonia

• carbon dioxide - from cellular respiration

• lactic acid - from anaerobic

• excess salts/ions - from food

• bile - from liver

• excess water - from water

✅✅excretory system - urethra

urine from the bladder goes down the urethra (a tube) where it is released into the external environment

✅✅excretory system - bladder

urine is stored here until it is ready to leave through the urethra

✅✅endocrine system - hormone types

• steroid hormones

  • derived from lipids (cholesterol).

  • nonpolar + hydrophobic → can cross a membrane

  • ex. testosterone, progesterone, cortisol

• amino acid based/peptide hormones

  • can be derived from amines (modified amino acids) or

  • can be derived from peptides/proteins (chains/polymers of amino acids)

    • peptide = less than 50 amino acids in its chain

    • protein/polypeptide = more than 100 amino acids in its chain

  • polar + hydrophilic → cannot cross a membrane

  • ex. adrenaline, thyroxine, insulin

✅✅endocrine system - signal transduction

• when a hormone signal is converted into a different type of signal in the receptors of the target cells

• only target cells with the correct receptor will respond to the hormone

peptide/protein hormones (ex. ADH, polar peptide hormone, can’t cross membrane)

1. hormone binds to receptor GPCR (transmembrane protein) on outside environment of cell membrane (→ receptor is extracellular) because shapes compliment each other. but this changes shape of GPCR

2. g protein (composed of 3 proteins - alpha, beta and gamma subunits) is attatched to GPCR on inside environemnt. it also changes shape, and alpha protein no longer fits, so detaches

3. the alpha g protein subunit attatches to adenylyl cyclase on inside environment which turns it into an enzyme

4. ATP then attatches to this enzyme, where it is converted into cAMP, a second hormone that is now in the inside environment.

steroid hormones (ex. testosterone, nonpolar steroid hormone, can cross membrane)

1. passes straight through cell membrane as it is nonpolar

2. binds to an intracellular receptor inside cell

✅✅regulation of blood glucose levels

• beta cells in pancreas (receptors) detect high blood glucose levels

• pancreas (also control centre) releaseses insulin hormone (endocrine system) into bloodstream

• insulin tells liver cells (effectors) to store glucose as glycogen + promotes uptake of glucose into muscle + fat cells → less glucose in blood

• liver can’t store glucose in liver because it is osmotic, meaning it draws water, so stores it as glycogen, a polymer of glucose

• insulin makes blood sugar level go down

• alpha cells in pancreas (receptors) detect low blood glucose levels

• pancreas (also control centre) releaseses glucagon into bloodstream

• glucagon tells liver cells (effector) to release glucose into bloodstream → more glucose in blood

• skeletal muscle + fat cells don’t release glucose back into bloodstream

• glucagon makes blood sugar level go up

• blood glucose spikes after a meal because the carbs are digested + absorbed as glucose into bloodstream

• low GI components of a meal take longer to digest, meaning there can be a rise in glucose levels after the first spike.

• glucose levels should be between 4 - 5.9 mmol/L

✅✅endocrine system - endocrine glands

• glands that produce hormones which are secreted directly into bloodstream (unlike exocrine glands which use ducts)

• hormones are signalling moleculules that travel through bloodstream and allow systems to communicate with each other. this regulates processes.

• because hormones travel in bloodstream, they are not super fast like nerves. instead, hormones are slower, longer-lasting and more general.

glands

• in brain

  • hypothalamus (master gland) - produces ADH, regulates temperature, controls pituitary gland (makes hormones to activate other hormones in pituitary gland)

  • pituitary gland - releases ADH, produces growth hormone, controlled by hypothalamus but controls many other endocrine glands

  • pineal gland - produces melatonin

• thyroid gland - produces thyroxine (regulates metabolism)

• parathyroid galnds - on other side of thyroid gland. produces parathyroid hormone

• thymus gland - produces thymosin

• adrenal glands - on top of kidneys, produces adrenaline + cortisol

• ovaries - produces oestrogen + progesterone

• testes - produces testosterone

• pancreas - produces insulin + glucagon

✅✅regulation of water balance

• when blood is too concentrated (not much water), osmoreceptors detect this stimulus (detect ion concentration/osmolality) + and send a message to the hypothalamus. the hypothalamus then sends a message to the release - the pituitary gland - to release more ADH in the bloodstream as a response. effector = aquaporins in collecting duct. also renin

• ADH makes collecting ducts in nephrons more permeable to water by creating more aquaporin proteins → more water is reabsorbed into bloodstream. + urine is more concentrated

• when blood is not concentrated enough (too much water) osmoreceptors detect this stimulus (detect ion concentration/osmolality) +, send a message to hypothalamus, which sends a message to the pituitary gland to reduce ADH release.

  • also, baroreceptors in arteries detect change in blood pressure which can indicate water loss

  • when barorecepters detect high bp → renin production reduced → renin release reduced → less angiotensin ii → lower bp

  • when barorecepters detect low bp → increased renin production + ADH + aldosterone (acts in DCT + collecting duct to increase reabsorption of water + sodium) → higher bp + water reabsorption + sodium reabsorption

✅plant systems - two types of vascular tissue

• xylem and phloem

• they transport nutrients + water around the plant

plant systems - systems in vascular plants

root + shoot system

• root system

  • organ = roots

  • roots anchor plant, absorb water from soil through osmosis, storage for plants. root hairs increase surface area.

• shoot system

  • organs = leaves + stems.

  • leaves are organ of photosynthesis.

  • stems support plant + vascular tissue travels through it to reach leaves

✅plant systems - vascular + nonvascular

• vascular

  • have transport systems for nutrients + water (xylem and phloem arranged in vascular bundles)

  • have two organ systems (root + shoot)

  • ex. trees, flowers

  • can be seed producing or seedless

    • seed producing can be flowering or non flowering

      • flowering can be monocots (parallel veins in leaves + scattered vascular bundles) or dicots (net like veins in leaves + vascular bundles towards outside of plant in stem + in middle in roots)

• nonvascular

  • no transport systems → rely on direct osmosis

  • ex. moss

✅plant systems - xylem tissue

• one way transport system

• transports water + dissolved minerals from roots → leaves. moves up stem through cohesion + adhesion (adhesion=water bonds to xylem tube walls, cohesion=water bonds to each other → this creates tension within xylem that helps move water upward)

• lignified cell walls (lignin deposited onto walls) → becomes dead, hollow, waterproof, hard, rigid cells + provides support

✅plant systems - phloem tissue

• two way transport system

• transports glucose made in photosynthesis from source cells (leaves) to sink cells (fruit, roots or tumours (carrot))

• living cells

✅✅plant systems - transpiration/evaporation

• stomata = openings in leaf surface (stoma singular)

• stomata allow carbon dioxide to enter and oxygen to exit by stomata cells opening, however this unfortunately lets lots of water escape through transpiration/evaporation as vapour (97% of water coming to leaves).

• guard cells of stomata need to be turgid (full of water) rather than flaccid (lacking water) in order to be open.

• if turgid, guard cells are hypertonic to epidermal cells. if flaccid, guard cells are hypotnoic to epidermal cells.

• because lots of water is lost through transpiration → water constantly needs to be brought to leaves to keep guard cells open

✅plant systems - water in animals vs plants

• animals dont have cell wall, so swell and burst when lots of waterenters

• plants have a cell wall, so dont burst when lots of water enters, but become turgid and have high turgour pressure.

✅✅plant systems - how do plants regulate water loss

• plants close stomata (by pushing water out of guard cells) when they need to conserve water which prevents water vapour being lost

• for example, no gas exchange happens at night meaning stomata can cose to conserve water

• water conservation is also needed when theres hot temperatures, a drought, etc

plant systems - vascular bundles/steles

in the cross-section of a dicot plants’ …

• roots - vascular bundle in the middle = stele

• stem - several vascular bundles around the outside with schlarenclyma

• leaves - vascular bundles running through midrib of leaves and then branch off into veins

• in dicot cross-section, phloem are smaller cells in the vascular bundle and located further from the centre of the stem than xylem vessels

• in dicot cross-section, xylem are bigger cells in the vascular bundle towards middle

✅plant systems - 4 forces in transpiration system (movement of water through xylem).

1. water moves in roots through osmosis. this pressure of water coming in moves water up

2. adhesion - attraction between water molecules + other surface. the narrower the surface, the stronger the adhesion force

3. cohesion - attraction of water molecules + water molecules.

4. transpiration/evaporation - water loss from stomata creates negative pressure at top of xylem vessels which pulls water up

✅✅plant systems - factors that affect rate of transpiration

✅plant systems - transpiration system vs process

system - movement of water from roots to leaves through xylem

process - when water evaporates out of leaves’ stomata

✅plant systems - translocation of sugars (movement of sugars through phloem)

• sugars are made in photosynthesis (glucose) in source cells (such as leaves)

• sink cells (such as stems, roots, fruit) need sugar to meet metabolic demands but cant produce sugars through photosynthesis

• sugars move from source cells → sink cells. can be up or down

• sugars first enter through companion cells and then into sieve tube members.

• Phloem near xylem → sugars/sap build up in phloem (high conc.) → water enters from xylem by osmosis → pressure builds → creates osmotic pressure (pushes sap along in wtv direction it was already going)

✅✅homeostasis

• the state at which the body’s internal environment is stable, despite many changes

• it can fluctuate, but within narrow limits

• the body’s goal is to maintain homeostasis via negative feedback loops

✅✅regulation of body temperature

• a negative feedback loop, nervous + endocrine if physiological

• can be physiological mechanisms response (involuntary)

• can be behavioural response (voluntary, ex. herding, moving into shade)

• can be structural adaptations (ex. small size → SA:V ratio, insulation)

• can be a combination

• poikilotherms - animals that don’t use physiological mechanisms to regulate body temperature as there is a reduced need to keep temperature within narrow limits → body temperature changes with environment throughout the day

• homeotherms - animals that use physiological mechanisms (aswell as the others) because they need to keep their body temperature within narrow limits → environment changes but body stays around the same

stimulus - body is too hot (above 36.7 degrees)

receptors - thermoreceptors in hypothalamus detect high body temperature

control centre - hypothalamus sends nervous signals to sweat glands

effector - sweat glands release sweat

response - body sweats, this counters stimulus (one example)

stimulus - body is too cold (below 36.7 degrees)

receptors - thermoreceptors in hypothalamus detect low body temperature

control centre - hypothalamus sends nerevous signals to skeletal muscles

effector - skeletal muscles move

response - body shivers (movement uses ATP, this releases heat), this counters stimulus (one example)

✅✅homeostasis - negative vs positive feedback loops

negative - through stimulus response model, body detects a change and gives a response that counteracts the stimulus, bringing the body back to homeostasis. most feedback loops are negative, example = body gets a bit cold so is made a bit warmer.

positive - through the stimulus response model, the body detects a change and gives a response that amplifies the stimulus, moving the body further from the original state. examples = cervix stretches more during birth, temperature keeps rising when you have a fever

✅✅homeostasis - stimulus response model

can be nervous or endocrine stimulus → receptor detects + sends message to control centre (endocrine gland, often hypothalamus or pituitary gland) → control centre sends message to effector → effector gives response

✅✅homeostatic malfunctions

• if homeostasis is not restored (homeostatic malfunction) → results in disease or death

✅✅homeostatic malfunctions - hyperthyroidism

• thyroid gland in neck produces too much thyroxine, negative feedback loop not working

• speeds up body’s metabolism too much

• often a result of graves disease, an autoimmune disorder, where b lymphicites make antibodies which attatch to + stimulate TSH receptors on thyroid cells → produces lots of thyroxine

✅✅homeostatic malfunctions - hypoglycaemia

• blood glucose level is too low

• often results from overcorrecting diabetes through medication

• reactive hypoglycaemia - when blood glucose spikes, it is brought down way too low aka sugar crash, can happen to anyone

✅✅homeostatic malfunctions - diabetes

• diabetes - disease where there is too high blood glucose levels.

• type 1 - an autoimmune disorder in which cytotoxic t cells mistake beta cells in pancreas for foreign objects so destroy them. this results in small or no amounts of insulin produced by the pancreas → high blood glucose levels → people inject themselves with insulin

• type 2 - insulin resistance in bodies’ cells, particularly liver. insulin is still produced, but isn’t responded to → high blood glucose levels → even more insulin is produced and this wears out beta cells and they die which makes it worse because now less insulin is being produced → people treat it with medication + diet to lose weight

• symptom = hyperglycemia - too much glucose in blood. means glucose cant reabsorb anymore into blood in nephrons → glucose in urine