Biodiversity (plants) Flashcards
Define being alive
Need to capture resources from environment, grow + reproduce yourself
Which kingdoms are contained within Eukarya?
Protista, Chromista, Plantae, Fungi, Animalia
LUCA
Last universal common ancestor
- possesses characteristics shared by all living organisms today
- has DNA, RNA, proteins, cell mem., systems for capturing light energy, carbs + enzymes
2nd law of thermodynamics
Total entropy of isolated system can only increase over time (order->disorder) so life uses energy to maintain + reproduce itself in orderly fashion
Stanley miller experiment
1953 heating cooling mimicked conditions Earths est. 4 billion years ago.
Methane, hydrogen, ammonium -> organic matter (glycine produced)
so simple chemicals need energy to form complex structures
Chemotrophs
Harness energy from chemicals (use ATP), reactions all exothermic
Peter Mitchell Nobel prize 1978
Chemiosmotic hypothesis - energy harnessed by ETC + used for H+ pump to set up pH conc. gradient so h+ diffuse through F type ATPase
feature of LUCA + found in Archaea +Bacteria
- needs oxidants + reductants
Archaean photosynthesis
Bacteriorhodopsin (retinal) has red colour + used to store photons (energy), cis-trans isomerisation driven by light moves 2H per photon
Bacterial photosynthesis
Uses chlorophyll, has photosynthetic reaction centres which absorb light resulting in e transfer along ETC
What are the two types of bacterial reaction centres?
Fe-S (found in green sulphur bacteria + heliobacteria)
Fe (cytochrome) can bind to H2S (found in purple sulphur + green non-sulphur bacteria)
*cyanobacteria only bacteria to have both types of reaction centres
How did oxygen evolving complex form?
Lateral gene transfer -> reaction centres combined + began to work together
allowed oxidation of water
Evidence for oxygen production in cyanobacteria
Fossils - stromatolites formed by growth of microbial mats w/ bands of iron oxides
Oxidation of metals -> O2 in atmosphere
Huronian Ice age after oxygen, as CO2 formed + is weaker than methane (CH4)
Pros and cons of oxygen
Pros - ozone layer forms preventing UV reaching surface allowing life outside of water
Cons - superoxide (free unpaired e), hydrogen peroxide (reactive, used in bleach, hydroxyl radical (very reactive) - Fenton reaction
Phagocytosis (1st heterotrophs)
aerobic respiration more efficient so allows cells to evolve + engulf smaller ones
When did complex structures appear in eukaryotes?
2 billion yrs ago, from Archaea
- Lokiarchaeota possess traits of eukaryotes including phagocytosis
Mitochondria + chloroplasts result of single endosymbiotic event
archaea consumed aerobic proteobacterium + cyanobacterium
Sexual reproduction green alga (Chlamydomonas reinhardtii)
Haploid most of the time, mitosis gives 4 daughter cells, reproduce sexually when stressed
Two types of gametophytes (mt+ and mt-)
Forms persistent zygospore - diploid, inactive
First land plants (pros and cons)
Coincided w/ increased O2, followed Cambrian explosion
Pros - new spaces, higher pCO2
Cons - lack of water, no current to aid reproduction
Give examples of bryophytes
Liverworts - dominant gametophyte, rhizoids grow down + absorb water, sperm swim form male to female gametophores so sporophyte grows on gametophore
Stomata + vascular tissue in mosses + hornworts
Moss - more complex leaf structure , simple water conducting tissues, ombotrophic (absorbs nutrients from water), sporophyte grows well above gametophyte
Hornworts - presence of cyanobacteria in clefts, symbiosis w/ nitrogen fixer
Problems with bryophyte
Poor ability to capture + retain water, poor water transport + limited uptake of nutrients, limited height so needs to be near surface
Rhynie Chert
410 Mya, fossils studied by Lang
preserved fossils of different species
features include vascular bundles, mycorrhizal associations (symbiotic relationship)
Lycopodiophyta
inc. spike moss, quillwort, clubmoss (not mosses)
-> reproduce by spores, alternation of generations, sporophyte dominant + photosynthetic
*increasing development of larger more dominant sporophyte
Tracheids
Type of water conducting cell in xylem, found in vascular plants
1’ growth cell division at tip - cell elongation
2’ growth cell division at cambia, structures become thicker eg. lycophytes evolved thick stems w/ lignin
Carboniferous forests
360-300 Mya formation of Pangaea extensive lycopod forests
Changing atmosphere as CO2 levels dropped
led to rise of megaphylls (leafy plants)
Horsetail innovations
Ring of xylem - better water transport + branching
Extensive roots (rhizomes) - better water uptake, vegetative spread, deciduous
Reproductive structures - strobili cone like structure produces spores
Ferns (pteridophyta)
Have rhizomes + vascular tissues, megaphylls
During reproduction, archegonium contains egg and antheridium encapsulates sperms
Progymnosperms e.g Archaeopteris
reproduce by spores/gametophytes like ferns but has ring of vascular cambium - wood
What caused fall of lycopods
Replaced by gymnosperms (naked seed) in the Permian due to new drying climate w/ Pangea formation opposed to warm wet tropical carboniferous
How do cones and seeds work?
Cones - seed matures in female cone + pollen released from male cone, controlled seed release leads to embryo
Seed- nucellus from mother feeds embryo + protected by seed coat
Cycads
1st dominant gymnosperms, dioicous, drought tolerant, slow wood production
Ginkgophyta
Dioecious, deciduous, fleshy seed wall, branching
Pinophyta (conifers)
often monoecious, single extant order (pinales), long lived, grow fast + big, woody branched trees
Gnetophyta
3 families v. different to one another, share feature w/ flowering plants
Angiosperms
cased seeds protected by ovary, endosperm acts as storage tissue that feeds embryo, flowers innovated, capable of double fertilisation
have xylem which are wider but prone to embolisms
male + female organs found together
Most primitive angiosperm
Amborella - has flowers but no vessels (only tracheids), dioecious, females have staminodes (infertile stamens)
Evolution of fruit
resistant seeds tolerate gut environment so are spread + germinate w/ fertiliser, not exclusively angiosperm but mainly
3 plants that have developed different methods to reach canopy?
Epiphytes, climbers, hemiparasites (root into stem of host + connect to xylem)
Plants with short life span
Ruderals - weed species (short-lived) that exploit gaps in ecosystem/disturbance e.g. poppies
Ephemerals - annual/perennial, grow following rain, persist as seeds or bulbs/roots
Adaptation to manage low water in deserts
Biochemical convergence - CAM photosynthesis prevents water loss by closing stomata during day
What are cotyledons?
‘seed leaves’ produced in embryo w/ different structure to actual leaves
angiosperms - monocots, dicots
Key fungi features
Hyphae - tubular filaments divided by septae into separate cells, cell walls contain chitin, growth from tips
Mycelium - mass of hyphae, denser mycelium forms mushrooms, large SA:V increases absorption
Saprotrophs
secreted enzymes decompose dead organic material
Mutualism-parasitism continuum
Fungi are both:
Mutualists - arbuscules exchange phosphate for assimilated carbon at root cell plasma membranes
Parasites - hyphae grow into hosts + manipulate to yield more nutrients (biotrophs) or kill it and live off of remains (necrotrophs)
