Bio life's complexity Flashcards
Linnaeus System
System used to organize and characterize different organisms
Fossils
Fossil records serve as EVIDENCE explaining the past
E.g. Tongue stones identified as fossilized teeth from ancient sharks.
What did Mary Anning suggest?
ANimals could go extinct
Lamarckism
Jean baptiste lamarck argued that organisms could acquire CHARACTERISTICS in their lifetime to ADAPT to their environments
Evolution definition
Cumulative change in GENETIC COMPOSITION of a population over time
Darwins 3 major propositions
1.Species aren’t immutable(unchangeable)
2.Descent with modification
3. Natural selection
1 of 3 of Darwin’s propositions: Descent with modification
Related species sharing a common ancestor will DIVERGE from one another gradually over time
Based on idea that trait inheritance occurs with modification through many generations
E.g. Homologous structures
1 of 3 of Darwin’s propositions: Species aren’t immutable
Populations show PHENOTYPIC variations within species and can change over time
E.g. Snapdragon colors and Flinch beak size
1 of 3 of Darwin’s propositions: Natural selection
Some individuals have an advantage and are more like to SURVIVE and reproduce passing down the PHENOTYPE
E.g. Adaptation of ground flinches for different food sources(seeds)
Speciation
- Evolutionary consequence of Reproductive isolation
- Lineages separate and are UNABLE TO INTERBREED despite common ancestor due to DIFFERENT SELECTIVE PRESSURES causing diversion
3 factors determining how close species are related to each other
- Genetic information
- Fossil record
- Morphological traits
Phylogeny
Shows the evolutionary relationship
Macroevolution
Explains evolutionary changes among large taxonomic groups above the species level including the:
ORIGIN EXTINCTION DIVERSIFICSTION of species over a long period of time
can Morphological traits be used to build phylogenies?
Yes
Monophyly, Polyphyly, Paraphyly are subgroups of what?
The Phylogenetic tree
Includes Common ancestor + ALL descendants
Polyphyletic group
Does NOT include the Common ancestor
Paraphyletic group
Includes COMMON ANCESTOR but not all the descendants
Taxon
Refers to the entities on the tree(e.g. humans and gorillas)
5 agents of evolutionary change
- Recombination
2 Gene flow - Natural selection
- Mutation
- Genetic drift
2 sources of DNA damage
- Exogenous(UV, Chemical mutagens)
- Endogenous(Reactive O2 species, hydrolysis, alkylation, endonucleases)
Low and High rate mutation drawbacks
High rate: Too many functional elements disrupted less fit organism
Low rate: No adaptive evolution
Population definition
Group of individuals that share GENETIC INFORMATION + from the same species
Gene pool definition
SUM of GENETIC INFORMATION(genetic composition) that is carried in the population
Genetic drift
Random sampling of alleles across generations
It is more influential in small populations
Stochastic changes(Type of Genetic drift)
Allele frequency changes from one generation to the next.
It REMOVES Variation, does NOT ADD
Microevolution
- Evolution within species that can be observed DIRECTLY acting upon natural populations
- Microevolutionary process can be INFLUENCED by agents of change
Adaptation vs Natural selection
Adaptation:
- Refers to a TRAIT
- Advantageous mutations can contribute to trait’s adaptiveness
Natural selection:
- Is a process
- Acts to select the Advantageous and deleterious mutations
Artificial selection
Manipulating via selective breeding
Plant populations(Non-randon mating)
- Most plants produce Male and Female gametes to MATE with themselves
- Plants with flowers have TIME POLYMORPHISMS(some plants flower earlier)
Gene flow
- Interbreeding occurs between 2 populations sharing GENETIC MATERIAL with distinct GENETIC COMPOSITION.
- Involves dispersal of individuals across space + successful breeding in new location
- Barriers reduce gene flow
E.g. pollen to new location or people moving countries
Pollen gene flow
Pollen contributes to gene flow in plants.
Flower color is determined by MULTIPLE GENEs
Impact of gene flow on gene pool depends on…
- Genetic differences between population
- Level of migration. movement or hybridization
(look at notes for further info)
5 Real deviations from Hardy-Weinberg
1 Migration occurs
2 Dna mutates
3 Population size is finite
4 Non-random mating
5 Fitness varies across the population
Speciation
Evolutionary process that forms new species through reproductive isolation causing 1 evolutionary lineage to split into 2 or more lineages of distinct from all other species
Allopatric speciations
Ancestral population divided by PHYSICAL BARRIER preventing reproduction and gene flow
Requirements of speciation
Genetic change to accumulate and differ between populations(both allopatric and sympatric)
Sympatric speciation
Ancestral population divided WITHOUT Geographic barriers due to
Bahevours or shape flowers
Fixed
All individuals in population/species are homozygous for that version
What are the 2 types of Reproductive Barriers?
Prezygotic
Postzygotic
What do reproductive barrier do?
Enables SPECIATION and PREVENT Gene flow
Prezygotic isolation
Barriers to reproduction BEFORE the union of nuclei
Postzygotic isolation
Barriers to reproduction AFTER union of nuclei
Types of Prezygotic isolation
- Geographic isolation
- Gene flow can be prevented by islands - Mechanical
- Some pollinators are specific to each flower differing in shape - Behavioral
- COURTSHIP in birds , calling in different frequencies - Mating time differences
- Corals release gametes that survive for short periods of time and spawn at different times - Ecological differences
- Cichild fish evolved to live in different ecological NICHES in Lake Mawli
Types of postzygotic isolation
- Fertilized egg/Offspring inviable
- Hybrid embryos formed by RANA species of frog are defective - Interbreeding
offspring can be viable but STERILE
Chromosomal rearrangements
Promotes speciation
sometimes 3 chromosomes(A, B, C can) can be differently paired, e.g. A+B or B+C individually becoming fixed and normal pairing of the 2 groups CANNOT OCCUR in hybirds
Species
Groups of actually or potential interbreeding natural populations that produce FERTILE offspring
Fertile hybird
Hybrids from parents interbreeding and that can produce offspring.
Adaptive Introgression
Fertile hybrids resulting from transferring pre-adapted traits from 1 species to another
Use of fertile hybrids
To breed endangered species like florida panther with texas pumas,.
Example of adaptive introgression
Humans x Neanderthals leading to inheritance of beneficial variation from related species accelerating adaptation and survival in new environment
Incomplete lineage sorting hypothesis
Alleles predating the speciation of neanderthals and humans, by chance or drift, these alleles were LOST in African humansBa
Negative frequency dependent selection
PREVENTS 1 phenotype dominating the others and becoming “FIXED”
Occur when RARE phenotypes have higher fitness than common ones, they will have strong selective advantage preventing from going extinct.
Example of Negative frequency dependent selection
Lizard males displaying behavioral variations
- Orange males: Aggressive, defend territory
- Blue males: Less aggressive with small territories but GUARD females
- Yellow males: Similar coloration to females and sneak around
What kind of model system is Negative frequency dependent selection
CYCLIC
It fails to reach Evolutionary Stable State with consistent phenotypes, the balancing selection occurs to maintain allele frequencies in population
Heterozygote advantage + name a example
Heterozygous individuals have fitness advantage against homozygous individuals.
Example: Sickle cell anemia heterozygous will be invulnerable against Malaria
Relative fitness(w) definition
Describes the success of other genotypes in the population and ranges from 0-1.0
Intersexual selection definition
Mate choice, choosing mates on certain traits
e.g. Females mating with Male birds with the longest male
Intrasexual selection
Individual competition of the SAME sex competing for access to mates including:
- Physical combat
- Displays of strength
Intersexual selection mechanisms
One sex(mostly females) hold preferences for specific traits
Traits that are costly to bear indicate the QUALITY of the male
These traits may become exaggerated and will be balanced by sexual and natural selection
Sexual dimorphism
Sexes of the same species exhibit different morphological characteristics
What traits enhance competitiveness(2)
Size and Behaviors
What are used to avoid costly fights in intrasexual selection
Rituals like Roaring and intimidation tactics(which sometimes are bluffs like hollow large claws)
What are some Sexual Conflicts between the sexes?
- Whether mating occurs
- Female mating frequency
- If sperm is used in fertilization
What do the 2 sexes do to resolve conflict? Give an example
Evolve traits to resolve conflicts in their favor
Pantry moth males with GIANT SPERM PACKETS trick females into thing that she is full so she doesn’t mate with anyone else. Laying eggs for his sperm.
The females evolved Genital teeth piercing the SPERMATOPHORES undoing the manipulation
Red queen hypothesis + example
Species must constantly adapt & evolve to survive while pitted against ever evolving species
Pathogens evolve to ether host and hosts evolve to avoid pathogens
Predator and prey interactions like cheetahs and springboks
What cycle does coevolution create
A continuous cycle of ADAPTATIONS & COUNTER ADAPTATIONS.
Each species exert a selective pressure on each the other
Driving force in evolution of species shapes behaviours, physiology and ecological relationships
Coevolution
Process of 2 or more interacting species(could be the same species) affect each other’s EVOLUTION through natural selection
They reciprocally affect each other’s evolution through the process of natural selection exerting selective pressure on each other.
Adaptation selects for counter adaptation which selects for adaption.
3 types of coevolution
- Host-parasite interaction
- Mutualistic coevolution(plant-pollinator)
- Plant-herbivore interactions
Maladaptive traits
Traits that harm survival
Ornament vs Armament traits
Ornaments:
Used to attract mates, animals may shake, lengthen or spread their ornaments.
Armaments:
“weapons” that have evolved for intrasexual selection for access to opposite sexes.
5 Antagonistic evolution
- Predator-prey
- Plant herbivore
- Host-parasite
- Brood parasitism
- Plant height
Plant herbivore interactions(Caterpillars and milkweed)
E.g. Monarch butterflies EXCLUSIVELY lay eggs on Milkweed species for the hatched caterpillars to eat.
There’s selective pressure on Milkweed to reduce herbivory.
- The milkweed evolved HAIRY LEAVES but caterpillars shave the hair before eating leaves.
- Milkweeds then evolve STICKY LATEX but caterpillars then attack leaf veins to turn off wax tap
- Milkweed evolved TOXIC CHEMICALS but caterpillars evolved ability to use that that chemical for their own defenses
Host-parasite interactions
Myxoma virus
Virulence level must suit rabbit: Killing too quickly reduces transmission
Immune evasion
Rabbit
Increased genetic resistance to virus
More effective immune response
4 Mutualistic Coevolution
- Plant pollinator
- Cleaning
- Endosymbiotic
- Defensive
plant pollinator interactions
Plants evolve NECTAR to entrance and reward insects to visit & sprinkle their pollen to other plants
Homologous characters
Characters derived from a COMMON ANCESTOR
e.g. bones in birds and bats
The sequence of DNA from species of 2 species share some similarities
Interspecies hybrid allow Genetic analysis
Humans can intervene and hand pollinate 2 flowers that have been reproductively isolated.
Example 1 : YUP(Yellow upper Petal) gene
- Illustrates how genetics can be used to REDUCE adaptive traits into their component Genetic Loci.
- Identifies speciation genes(speciation involved in speciation)
- Allows to understand how traits can evolve via mutations
Example 2: melanism of peppered moth
Industrial revolution led to darker trees which meant that darker moths better at camouflaging(selective advantage)
- The gene CORTEX, large insertion caused by TRANSPOSABLE DEMENT HOPPING into the 1st intron
- DNA divergence estimate gene arose -1819
Example 3: Vinegar fly
- Allelic series of Cyp6g1 features transposable elements and gene duplications
- insecticide resistance risen through GENE DUPLICIATION & TRANSPOSABLE
How do population structures arise
Refers to distribution of individuals
- arise when Demographic processes produce systemic differences in allele frequencies between subsets of a larger population
- May arise from ISOLATION or NON RANDOM MATING
- Population structure influenced by ALL AGENTS OF CHANGE
Location of Gaseous exchange in fungi, unicellular organisms and plants&animals
Cell membrane(Cell wall) - unicellular organisms
Body wall - fungi
Specialized respiratory structures - plants & animals
Features of Gas exchange
- High SA/volume ratio
- Partial permeability allowing selected materials to diffuse in
- Very thin for short diffusion pathway
- Movement of external medium(AIR)&internal medium(blood) maintain concentration gradient
Components of Fick’s law
(SA x Partial pressure x Diffusion coefficient) / Diffusion distance
2 types of stomata
Kidney shaped and Dumbbell shaped
Kidney shaped stomata
Formed on leaf epidermis without predetermined location
Dumbbell shaped stomata
- Next to subsidiary cells
- Collectively are STOMATAL COMPLEX constrained at the leaf base with STOMATAL PORES formed adjacent to leaf veins
Factors affecting stomatal density
- Temp
- Humidity
- Partial pressure of gases
- Different leaf type or places on plant as conditions change throughout growth
Do plants have specialized network of gas exchange?
Each area of the plant takes care of its own gas exchange needs.
Where can the stomata be found on?
- Stems
- Petals
- Leaves(highest leaves, high metabolism + photosynthetically active) Has SA/V ratio
- Roots, root hairs can exchange gas, H2O, nutrients
Other features enabling efficient gas exchange
AERENCHYMA
- Living cells have part of membrane exposed to air(loosely packed)
- Leads to rapid diffusion in intracellular area of plant
- Relies on PRESSURE gradients to drive gases from High to low pressure.
- Cells live close to surface reducing the distance gas has to travel inside plant
- Forms when cells separate or collapse
LENTICIL
- Small pores allowing gases in&out to interact with living tissue
- Found in woody stems and shoots(photosynthesize less)
Characteristics of wetland plants
Due to LESS gas exachange in air
Air enters through COMMON REEDS from broken stems or dead plants connected by underwater structures(RHIZOMES) that grow horizontally below the soil
Which type of animals avoid the need to specialized structures in moist and aquatic environments
Animals with THIN Tissues rely on O2 diffusion. Long thin bodies
Co opt other structures with large SA to aid in gas exchange(Feeding tentacles)
E.g. Annelid, Nematode, Platyhelminth
Gas exchange in fungi
- Lack specialized gas exchange structures
- Gas exchange requirements low -> Dormant for long periods
Yeast(Unicellular):
Switch between Aerobic & Anaerobic baed on O2 availability
Multicellular:
Takes place via Large branching network of MYCELIUM possessing microscopic HYPHAE extending into small crevices in soil to interact with air pocket
Ventilation
Gases moved across gas exchange surface via BODY MOVEMENTS or movement of respiratory structure to optimize Pressure gradient + Increases rate of diffusion across gas exchange surface
Circulation
Gas moves from To & FROM has exchange surface and body tissues.
Can occur via dissolution into a circulatory fluid(Blood) or DIRECTLY via network of branching tubes
Terrestrial environments
O2 availability high but h2o loss is problematic
Gas exchange structure characteristics
- Respiratory surfaces stay MOIST
- Terrestrial animals have INTERNAL gas exchange structures
Gas exchange for insects
Gas exchange system:
- Utilizes network of tubes called TRACHEA
- Trachea allows DIRECT O2 delivery to tissues & cells
Air enters body through SPIRACLES(small openings)
located on sides of Thorax&Abdomen into the
Tracheoles -> individuals
-Insects can CLOSE spiracles to prevent H2O loss
- Contract abdomens to VENTILATE, sucking in air + O2 inside the body
Large SA allows O2 down & CO2 up of cells
Gas exchange in Rabbits
- Vascularized lungs
- Air -> Nose/month -> Branching into Bronchi -> Bronchioles(for animals with high O2 requirement) -> Alveoli
- Thin lung wall + surrounded by capillaries to transport O2 in & CO2 out of body tissues
- Lungs branching network = High SA for gas exchange.
- Kept moist by surfactants secreted by pneumocyte cells
What do surfactants do
Reduce surface tension of lung aiding in diffusion of gases
Gas exchange in birds
- High rate of gas exchange due to High oxygen requirements; increases Dramatically during flight
- Unidirectional flow of air ventilated by Air sacs pumping air to & from lungs in specific orders
-> Fresh air passes over gas exchange surfaces during inhalation & exhalation(constant supply of fresh air)
Parabronchi
- Found in birds
- Increase SA interacting directly with large capillary network to exchange gases transporting them around the body.
- Lungs DONT move
Gas exchange in Aquatic species
Made of individual filaments covered in Lamellae to increase SA for gas exchange
O2 diffuse from H2O -> blood in the gill capillaries
CO2 diffuses from body-> H2O to be expelled
Why do internal gills employ countercurrent exchange mechanism?
Internal gills employ countercurrent exchange mechanism :
where blood& H2O flow in OPPOSITE directions maintaining conc gradient to maximize O2 uptake and CO2 removal
Autotroph vs Heterotroph
Autotroph:
Self produces majority of nutrients required for cellular respiration
Heterotroph:
Obtains majority of nutrients from other organisms
Autotrophic adaptations(plant, algae, photosynthetic bacteria)
Capture sunlight(chemical energy) & fix it into organic compounds in specialized organelles(chloroplast)
-> calvin cycle converts CO2 to Glucose
A type of heterotrophic
How do hydrothermal vents(Autotroph) convert carbon to food?
Oxidation of inorganic nutrients via CHEMOSYNTHESIS by bacteria in host
Heterotrophic adaptations
adaptations to collect and capture food:
- Modified mouth/limbs(sucking, chewing, siphoning, sharper claws, increased mobility)
adaptations for chemical digestion:
- Fungi: break down decaying matter via secretion
- Plant parasite: Invade vascular tissue of plants uptaking key nutrients + transferring RNA & pathogens
- Carnivorous plants - Chemical or physical signal to attract their prey + digestive enzymes
Where does nitrogen fixation occur
Plant nodules(specialized root structures) where rhizobia fix N2 & receive nutrients
Rhizobacteria
Live in association with plant Roots. Plants give them nutrients, in turn they:
Produce Antibiotics
Absorb unwanted chemicals form soil
Facilitate acquisition of essential nutrients
Mycorrhizae fungi and plants relationship
Mutually beneficial, the Mycorrhizae receive nutrients from the plant and in turn:
- access nutrients(phosphate, cu, zn) in soil normally unavailable for plants
- Acts as physical barrier against pathogens and produce antibiotics
How do plants excrete metabolic waste
Via transpiration from leaf stomata
Lenticels
Permanently open pores on stems and bark provide another pathway to remove H2O gases and gases
Explain the movement of stomata and how it affects metabolic waste during the day and night
Day - Stomatal transpiration balances the H2O in plants
Night - Stomata closed, excess H2O and minerals in tissues, there’s continued absorption of water from soil due to ROOT PRESSURE
Guttation
Some plants excrete excess H2O & minerals in small droplets of Xylem Sap exuded from leaf margins
Occurs when Root pressure > Transpiration, forcing out xylem sap through secretory cells in leaf epidermis called HYDATHODES(evolved stomata)
What are the 2 destinations of amino acids in plants
- UREA as nitrogenous waste
- May be reused for protein synthesis for protein synthesis ->Growth & Development
Where to plants store unwanted metabolic byproducts?
Cell’s vacuoles in the form of AA, Salts, H2O.
They can buildup in tissue which is later SHED from plant as Fruit, leaves, bark
Macro nutrients(4) for plants
Large amounts of it required
Carbon(from atmosphere): Proteins, Nucleic acids, Carbohydrates
Nitrogen(from atmosphere): Nucleic acid, Proteins, Chlorophyll
Potassium: Gas exchange regulation
Micronutrients for plants
Cl
Fe - Mitochondria & Chloroplast cofactor
Mn
Cofactors* = substances aiding enzyme function
What do animals digest Carbohydrates, proteins, lipids, what is:
Glycogen
Disaccharide
Proteins
Lipids
broken down to?
Glycogen: Glucose broken down to Pyruvate + ATP + NADH
Disaccharide: Fructose + Glucose
Proteins: AA gets deaminated then use to glycolysis for citric acid. AA can be used to make new proteins
Lipids(triglycerides) -> Glycerol+fatty acids -> Acetyl CoA via Beta-oxidation-> Citric acid cycle
Heterotrophic fungi
Detritivores or Decomposers recycling nutrients into soil or directly to plants. Getting carbon compounds from non living organic substrates or living material via nutrient absorption across CELL wall.
Multicellular fungi vs Unicellular yeast food sources
Multicellular fungi: Hyphae grows into food source
Unicellular yeast: Become colonial to take advantage of food source
Fungi digestion for macromolecules+insoluble polymers and small molecules
Small molecules(sugars, AA)
accumulate in watery film surrounding the hyphae or yeast diffusing through the cell wall.
Macromolecules + insoluble Polymers(protein, glycogen, starch, cellulose)
undergo preliminary digestion then absorbed
How are macromolecules+ insoluble Polymers digested
Specific enzymes in exudate secreted by HYPHAE or YEAST facilitates breakdown of extracellular substrates and diffusion of products for digestion
Is the digestive system highly vascularized?
Yes
Foregut
Intake+Storage of food.
Initial stages of chemical and mechanical digestion
Midgut and Hindgut
Mostly chemical digestion +absorption of nutrients prior to defecation or evacuation of waste products
Herbivore gut adaptations
- Difficult + low energy food source
- Mechanical digestion:
1. Mouth have teeth that can tear, crush grind, coarse plant matter
2. Stomach/crop: Very muscular so food can be squeezed and churned
Ruminants: Foregut ferments 4 compartments are
Rumen
Reticulum
Omasum
Abomasum
Rumination process
Food regurgitated from Rumen to Mouth for mechanical digestion passed through different stomach regions where plant matter is fermented by microbes
Hindgut fermenters
Somple stomach relying on LONG hindgut for CAECUM’s microbes to ferment plant food
Carnivore adaptations
- Mouth adapted to capture prey & tear flesh
- Rely more on chemical digestion(salivary enzymes + acidic stomach)
- Shorter and less complex
- Storage of food in digestive tract not required
- Lipid broken down in midgut via bile secreted
Nitrogenous waste
Ammonia must be converted either into UREA or URIC acid
How do aquatic animals release nitrogenous waste?
Release as NH3 into environment
NOT energy intensive as NH3 diluted to tolerable levels
How do Birds/reptiles/insects release nitrogenous waste?
Uric acid excreted in solid form and Most energy intensive
How do mammals and adult amphibians release nitrogenous waste?
Convert to urea(less toxic) requiring less H2O for removal and requires energy
Aquatic mollusks metanephridia
Type of excretory gland drains nitrogenous waste from sacs surrounding heart down into mantle cavity to convert it to NH3 rich urine
Which organisms excrete nitrogenous waste from gills
Fish Mollusks and crustaceans
Process of kidneys(3 steps)
1: Filtration
2: Reabsorption + secretion
3: Excretion
Explain kidney’s filtration process
Blood interacts with tubules via GLOMERULUS(collects larger molecules like blood and proteins). H2O + ions filtered into the tubule capsule/bowman’s capsule(collects AA, salt, glucose)
Explain kidney’s Reabsorption and secretion process
Blood flow through another network of capillaries that interact with Renal tubules to reabsorb and secrete solutes.
Altering composition of fluid in tubules, ION concentration increases as it flows towards COLLECTING DUCTS of kidney before excretion
Explain kidney’s excretion
Interaction between blood vessels and renal tubules in nephron ELONGATED & FOLDED to increase SA:V + diffusion rates
Freshwater vs Saltwater fish nephron
H2O balance for different fishes are different
Freshwater fish:
LARGER filtration to dilute urine in larger volumes
Osmotic conc. of bodies is higher than surroundings
Insects
Cells of tubules actively transport uric acid K+, Na+ from extracellular fluid into the tubules
High conc. of solutes in tubules causes H2O to flow osmotically flushing tubule content towards the gut
Epithelial cells of hindgut and rectum actively transport Na and K ions from gut back into extracellular fluid
Transport of salts create osmotic gradient pulling H2O out of rectal content
As uric acid conc. increases, it forms colloidal suspension freeing even more H2O to be absorbed
Loop of henle
Found in MAMMALS
Elongates of proximal tubule functions as counter-current multiplier changing conc gradient of the surrounding tissues
Extends into MEDULLA region of kidney
Signal
Acts/strategies INFLUENCING behavior of other organism(receivers).
They’ve evolved specifically because of the effect they have on intended receivers
E.g. Bioluminescence in elateroid beetles used as warning signals
Cues
Incidental source of info that may influence behavior of receiver despite not having evolved under selection
What are 6 modalities to discern cues from environment(CEMPMA)
Chemical
Electrical
Mechanical
Photic
Magnetic
Auditory
Chemoreceptors and its 2 pathways of activation
Chemical sensitive protein receptors activated through physical interaction with specific types of molecules
1. Direct activation
Opens channel in cell membrane
2. Indirect activation
Causes activation of another protein carrying the signal to open another protein channel
Thermoreceptor
Modified chemical sensors that change shape in response to temperature enabling passage of ions across membrane
Mechanoreceptors
Motion receptors
Motion sensitive proteins respond to mechanical signals(movement, strech, vibration) causing channels to open & ions to pass through
Photoreceptor
Light receptors
Responds to SPECIFIC WAVELENGTHS of light when a PHOTON bumps into photoreceptor protein. Protein absorbs energy & temporarily changes shape
What is the role of photoreceptor in plants
Mediate plant’s response to light(UV->IR) as it contains the protein component bounded CHROMOPHORE(light absorbing pigment)
Chromophore
Chromophore in a specific photoreceptor absorbs specific light wavelength -> structural changes in receptor.
Activation of photoreceptor triggers signalling cascade within plant cell -> gene expresssion affecting plant growth & morphology