unit 8 - botany Flashcards
what processes do autotrophs need gas exchange for
photosynthesis and cellular respiration
what processes do heterotrophs need gas exchange for
cellular respiration
how does gas exchange occur
- via diffusion
1. through a medium or from one medium to another
2. across membrane/surface
what is gas exchange
random movement of molecules from an area of high concentration to low concentration
4 properties of gas exchange surfaces
- permeable (gas can diffuse freely)
- large SA (SA to volume ratio)
- moist (gases can dissolve)
- thin (diffuse thru short distance)
why are leaves adapted for both gas exchange and water conservation
- chloroplasts require steady supply of carbon dioxide and oxygen produced must be removed but must avoid excess water loss
- must balance need for gas exchange with risk of water loss
waxy cuticle as an adaptation for gas exchange and water conservation in leaves
- secreted by epidermal cells
- waterproof layer, thickness varies depending on biome
- low permeability to gases, prevents water loss
guard cells (stoma) as adaptation for gas exchange and water conservation in leaves
- two guard cells cover pore called stoma
- close stoma at night when no photosynthesis and gas exchange and when plant is dehydrated
spongy mesophyll as adaptation for gas exchange and water conservation in leaves
- connected to outside air via stomata
- large SA for gas exchange
- walls permanently moist (from xylem) to allow CO2 to dissolve and enter cells
how is the concentration gradient maintained in leaf
- photosynthesis keeps concentration of CO2 in cells lower than outside
- O2 constantly being made, concentration in cells higher than outside
stomal density meaning
of stomata per unit area of leaf surface
how to calculate stomal density
mean # of stomata/area of field of view
how to use microscope to observe stomal density
- put layer of clear nail varnish under leaf and wait to dry
- put piece of tape over polish and peel off
- place tape on microscope slide, and look
- take measure of stomatal density
- find real size of image using diameter of FOV
plan diagram meaning
an image that shows overall tissues/structure in biological system instead of individual cells
how to spot epidermis of leaf
top (upper epidermis) or bottom (lower epidermis) of leaf, faces outside air
how to spot palisade mesophyll of leaf
long cylindrical cells, tightly packed under upper epidermis
how to spot spongy mesophyll of leaf
rounded cells with extensive space b/w them
how to spot guard cells
in pairs, surround a pore in the bottom of the leaf
function of epidermis
protection against damage and water loss
- creates waxy cuticle
function of palisade mesophyll
photosynthesis, it receives light through cuticle and epidermis
function of spongy mesophyll
photosynthesis and gas exchange
function of guard cells
open stomata to allow for gas exchange or close them to prevent transpiration
high humidity and leaves
air saturated with water vapour, water not lost through leaves because of similar concentration gradient
low humidity and leaves
water can evaporate in air spaces in spongy mesophyll and diffuse out of leaf because difference in concentration gradient is large
transpiration meaning
loss of water through leaves
what is transpiration rate affected by
environmental factors
1. temperature
2. humidity
how does temperature affect transpiration rate
- high temp = more energy available for evaporation
- warmer air can hold more water vapour before becoming saturated
how does humidity affect transpiration rate
- higher humidity = smaller concentration gradient of water vapour inside and outside of leaf <- lower rate of diffusion
- no transpiration if air outside leaf is saturated with water vapour
how is opening/closing stomata related to carbon dioxide concentraiton?
- aperture of stomate varies according to CO2 concentration <- if conc is high enough for photosynthesis, stomata can reduce opening to prevent water loss
what is a potometer
tool used to measure rate of transpiration of a plant
how does a potometer work
- leafy shoot placed in apparatus underwater, no air spaces
- rate in which bubble in tube moves measured using graduated capillary tube and stopwatch
- water in reservoir can be let into apparatus to push bubble back to starting point
why is waters property of adhesion important for plant roots
- water adheres to surface of soil particles
- plants take in this water via osmosis
what is capillary action
movement of liquid/water through a narrow space, often in opposition to external forces like gravity
adaptations of xylem to transport water through plant
- long tubular vessels in vascular plants
- cellulose in cell wall (helps water adhere)
- vessel walls thickened with lignin
what is lignin
parallel tubes of xylem with rings of a polymer (lignin)
why is lignin important in plants
- provides extra support for plant as it grows against gravity
- provides support against low pressures in xylem (prevents collapse)
how does adhesion work b/w water and walls of xylem vessels?
hydrogen bonds b/w water molecules and cellulose in xylem walls
why is cohesion essential for water transport in plants?
- hydrogen bonds b/w water molecules creates long chain from roots to leaves
- w/o this, column of water would break, trees wouldn’t grow as tall
the cohesion-tension hypothesis
- transpiration from stomata in leaves creates negative pressure
- transpiration pull creates tension, draws water upward in xylem
- cohesion: pulls water in chain as top-most water pulled out of stomata
- adhesion: water hydrogen bonds to xylem walls to crawl up xylem
what is a cotyledon
an embryonic seed leaf
- typically first leaves to appear from germinating seed
what do monocotyledons (monocots) have?
1 cotyledon, fibrous roots, parallel leaf veins, scattered stem vascular bundles, flower petals in 3s
what do dicotyledons have?
2 cotyledons, tap root, net leaf veins, vascular bundles form ring, flower petals in 4s and 5s
what are the tissues of the stem
xylem, phloem, cambium, epidermis, cortex, pith
xylem function (stem)
transport water from roots to leaves
phloem function (stem)
transport sugars from leaves to roots
cambium function (stem)
production of more xylem and phloem
epidermis function (stem)
waterproofing and protection
cortex function (stem)
support and photosynthesis
pith function (stem)
bulking out the stem
gametes of plants
male type: pollen
female type: egg
where are male gametes found in flower
in pollen grains on anther
where are female gametes found in flower
in ovules in the ovary
production of pollen (male gametes)
- in anther, diploid cells go thru meiosis to produce haploid pollen grains
- in each pollen grain, the haploid nucleus creates 3 copies of self
- 2 are male pollen gametes
- 1 used for gene expression during pollen development and fertilization
production of plant eggs (female gametes)
- in carpel (pistil) ovary and stigma connected by style (hollow tube)
- ovary has 1+ ovules, and cell in center of ovule goes thru meiosis to produce 4 haploid nuclei
- each one divides 3 times by mitosis = 8 total
- 1 becomes egg
- others help embryonic development + fertilization
pollination definition
transfer of pollen from anther to stigma
how does pollination occur
- pollen grain on stigma grows pollen tube down to ovary and into ovule
- pollen meets with egg, fertilization occurs, zygote produced
what are perfect flowers
flowers with both “male” and “female” parts
what are imperfect flowers
more rare: flowers with either “male” or “female” parts
what are some common features of insect-pollinated flowers
large bright petals (landing stage), scent (attraction), pollen grains(large+sticky to attach to insects, good food source bcus protein), stigma (sticky to collect pollen), glands (food source for insects)
what is cross pollination
when one plant fertilizes another plant of the same species
how does cross pollination support hybrid vigor
offspring of unrelated plants of the same species tend to grow stronger
what is self pollination
plant pollinates itself or a different flower of the same plant
why could self pollination be a problem
- no genetic diversity
- recessive traits are amplified
- inbreeding depression (rare recessive genes paired together)
- heritable characteristics are amplified, less healthy
mechanisms evolved to prevent/reduce self-pollination
- pollinators, separation, timing, morphological
how do pollinators prevent/reduce self pollination
they facilitate the transfer of pollen via an outside agent (wind, bees)
how does separation prevent/reduce self pollination
separates anthers and stigma/styles/ovaries in different male and female flowers
how does timing prevent/reduce self pollination
anthers and stigmas mature at different times
how do morphological traits prevent/reduce self pollination
anthers and stigmas can be at different heights
what is self-incompatibility
pollen fails to germinate or pollen tube stops growing before reaching ovary due to rejection of self-proteins or cells (opposite of human immune system)
what is the s gene, what is it used for
gene with multiple alleles and is a genetic mechanism used by some plants to ensure self-incompatibility
- species with s gene, sexual reproduction can only occur thru cross pollination
what is seed dispersal? what is it used for
- when seeds travel away from parent plant
- used to reduce competition b/w parent and offspring to spread a species
four types of seed dispersal methods
- animals, seeds are attractive for eating or covered in hooks to catch fur
- feathery/winged to catch wind
- lightweight, waterproof, buoyant to float on water
- dry and explosive
what is seed germination
- sprouting of a seed, occurs after dispersion
what does seed germination require
- water
- oxygen
- warmth
how does seed germination work
- food reserves (starch) are mobilized, digested then transferred to the growing embryo
difference b/w breathing, gas exchange, respiration
breathing: physical process of inhalation and exhalation
respiration: chemical process of cells using oxygen and releasing co2 (cellular respiration)
gas exchange: diffusion of air from lungs to blood
what is ventilation, what is it used for
- expelling air and replacing it with fresh air
- prevents oxygen concentration from dropping to low
- prevents CO2 concentration from being too high
what is required for efficient gas exchange in lungs
- thin, moist lining
- good blood supply
- good ventilation
- large SA
movement of gases (gas exchange) in the alveolus
- high conc. gradient maintained
- breathing in increases conc. of O2 in alveoli -> diffuses into blood
- breathing out decreases conc of CO2 in alveoli -> diffuses out of blood
- no ventilation = no gas exchange
gas exchange in fish
- take in fresh water through mouth to pump over gills and out of gill slits
- one-way flow of water opposite to blood flow, maintains concentration gradient
2 things helping to maintain concentration gradient in lung
ventilation and constant supply of fresh blood
how does air move thru respiratory system
trachea->bronchi->bronchioles->alveoli
large SA as an adaptation for gas exchange in lungs
- alveoli increase SA, each has own dense network of capillaries
- each alveolus is very small, but many of them (300M)
- matches SA of capillaries
thin membrane as an adaptation for gas exchange in lungs
- pulmonary alveolus has diameter of 0.2-0.5μm, but wall is single layer of cells (0.2μm)
- capillary wall also single layer of cells
- reduces distance b/w air and blood
moist surface as an adaptation for gas exchange in lungs
- allows cells to secrete a pulmonary surfactant which has structure like phospholipids
- surfactant forms monolayer on moist lining walls with hydrophobic tails facing out
- reduces surface tension and prevents alveoli from sticking to each other when exhaling
- prevents lung collapse
important structural details of respiratory system
- trachea: rings of cartilage to stay open even in low pressure
- bronchi: rings of cartilage
- smooth muscle fibres allows for width of airways to change
- alveoli: gas exchange
- diaphragm: controls volume of chest cavity
if gas is free to move, it will always go from high/low pressure to high/low pressure
high, low
what happens during inspiration (inhalation)
- muscle contractions increase volume in lung cavity
- air pressure drops below atmospheric pressure (outside pressure)
- air drawn in lungs until pressure equalizes
what happens during expiration (exhalation)
- muscles contractions decrease volume of lung cavity
- air pressure rises above atmospheric pressure
- air pushed out until pressure equalizes
- helped by elastic recoil of fibres in lung tissue that stretch during inspiration
diaphragm during inspiration vs. expiration
i: contracts, moves down
e: relaxes, pushes up
abdomen wall muscles during inspiration vs. expiration
i: relax, allows diaphragm to push abdomen out
e: contract, pushing up (during forced expiration)
external intercostal muscles during inspiration vs. expiration
i: contract, pulls ribcage up and out
e: relaxes, in elongated state
internal intercostal muscles during inspiration vs. expiration
i: relaxes, in elongated state
e: contract, pull ribcage in and downwards (during forced expiration)
volume/pressures during inspiration vs. expiration
i: thorax volume increases, pressure decreases, sucks air in
e: thorax volume decreases, pressure increases, forces air out
what is tidal volume (TV)
amount of air that can be inhaled or exhaled during one respiratory cycle
what is vital capacity (VC)
total air exhaled after max. inhalation and vice versa
what is residual volume (RV)
volume of air remaining in lungs after max. exhalation
what is total lung capacity (TLC)
max volume of air lungs can accommodate
TLC = VC +RV
what is inspiratory reserve volume (IRV)
air forcibly inhaled after normal tidal volume
what is expiratory reserve volume (ERV)
air forcibly exhaled after exhalation of normal tidal volume
what is inspiratory capacity (IC)
max volume of air inhaled following resting state (normal exhale)
what is functional residual capacity (FRC)
amount of air remaining in lungs after normal exhalation
3 main types of blood vessels and their functions
arteries: carry blood away from heart
capillaries: used for exchange of substances
veins: carry blood back to heart
what is the tunica externa in arteries
- outermost layer
- tough layer of connective tissue w collagen fibres
what is the tunica media in arteries
- 2nd outermost layer
- thick layer of smooth muscle and elastic fibres
- made of protein elastin
what is the tunica intima in arteries
- innermost layer
- smooth endothelium forming lining of artery
what is the lumen in arteries
- space inside artery where blood flows through
- relatively narrow compared to walls
collagen fibres as an adaptation of the arteries
- tough rope like proteins with high tensile strength
- can withstand high and changing pressures w/o bulging or bursting
elastic fibres as an adaptation of the arteries
- stretches to increase lumen with each pulse of blood
- after pulse, fibres recoil decreasing lumen size
- reduces energy used to transport blood and maintains blood pressure
smooth muscles as an adaptation of the arteries
- contracts and relaxes to control diameter of lumen (vasoconstriction and vasodilation)
- allows body to adjust flow rate to certain tissues and organs
structure of capilaries
- diameter of 10μm, 1 rbc can pass thru at a time
- has single layer of epithelium cells
- capillaries branch and rejoin repeatedly to supply cells/tissues
arteries maintain high/low blood pressure and high/low velocities of blood flow
high, high
capillaries maintain high/low blood pressure and high/low velocities of blood flow
low, low
what is the basement membrane
single layer of endothelial cells, coated by a fibrous protein gel on the outside of capillary
what substances can/cannot pass through capillarie
can: O2, CO2, glucose
cannot: proteins, amino acids
what do pores do in capillary
b/w epithelium cells and allows fluid from blood to leak out through basement membrane
what is a fenestrated capillary
- capillaries with very large pores
- allows for large volumes of tissue fluid (part of plasma) to pass through, speeding up exchange
example of fenestrated capillaries
the kidney’s filtration system
structure of veins
- large lumen, low BP (no pulse), irregular bloodflow
- walls of veins are thinner + less elastic fibres+less muscle than arteries
how is blood flow in veins assisted
- assisted by gravity and pressure from adjacent tissues, especially skeletal muscle
- when surrounding muscles contracts, it become shorter and wider squeezing vein and pushing blood
how is backflow prevented in veins
- using valves
- if backflow begins, blood gets caught in flaps of pocket valves pushing it closed
- blood flows properly: pushes flaps to sides of veins and pocket valve opens
how are varicose veins caused
- when veins are weakened or valves damaged
- blood flows backwards and accumulates causing swelling and enlargement
- often occurs in legs
wall thickness of arteries vs. capillaries vs. veins
a: thick
c: one cell thick
v: medium
size of lumen of arteries vs. capillaries vs. veins
a: relatively small
c: tiny
v: large
cross section shape of arteries vs. capillaries vs. veins
a: circular
c: somewhat circular
v: somewhat circular
inner surface of arteries vs. capillaries vs. veins
a: corrugated
c: no corrugation
v: no corrugation
fibres in walls of arteries vs. capillaries vs. veins
a: visible fibres
c: no fibres
v: few or no fibres
what is a pulse, what is it caused by
- a vital sign used to describe a person’s heart rate
- cause by a push of pressure that stretches artery wall
how does a pulse oximeter detect pulse
- shines red LED light thru finger and detector measures how much light passes thru tissues
- measures variation in blood amount per heartbeat
how does a pulse oximeter detect % saturation of O2
- depending on how much light is absorbed
- deoxygenated blood absorbs red light
- oxygenated blood absorbs infrared light
what are coronary arteries, how many are there
arteries responsible for transporting blood to heart tissues
- 2, right coronary artery and left coronary artery
when does coronary occlusion occur
when a build up in the artery prevents ability to deliver oxygen and nutrients to heart
symptoms of coronary occlusion
heart pains, increased heart rate, shortness of breath, heart attack
how can fatty deposits harden in coronary artery, what does this lead to
- can be infused with calcium salts, creating rough inner surface
- damage to rough surface can trigger formation of blood clot (thrombosis) which can block blood flow to heart muscles
- causes heart attack (myocardial infarction)
what is atherosclerosis
- when fatty tissue called atheroma develops in artery wall, causing occlusion/blockage
what is coronary heart disease (CHD)
narrowed or blocked coronary arteries
risk factors of coronary heart disease (CHD)
- hypertension, high salt intake, genetic predisposition, old age
- the other obvious ones
