Plants Flashcards
Heterotroph
respirates, but does not fix carbon eg. humans
Autotroph
self feeders eg. plants
Length of time ago plants formed
> 3.5 million years ago
Stromatolites
structures built from cyanobacteria
Banded iron
formed from free oxygen reacting with free iron in water
Consequences of oxygen accumulating in the environment
- anaerobic organisms unable to survive
- reacts with methane, creates CO2, cools Earth, causes Huronian Ice age
- ozone created by oxygen rising high in the atmosphere and being hit by UV radiation
oxygen-breathing organisms are able to form
Chloroplasts
type of plastid containing chlorophyll, where photosynthesis takes place
Endosymbiosis
cyanobacteria engulfed by amoeba-like eukaryote, kept alive, plastids transferred to host
Evidence of endosymbiosis
- plastids have double membrane
- plastids have own DNA
- plastid DNA is ring structure, not chromosomes
plastids have similar structures to cyanobacteria (thylakoids = membrane structures containing chlorophyll) - plastid DNA related to cyanobacteria DNA
Why genes are lost
- not needed
- transferred to host nucleus
- redundancy as host has same gene
Photosynthetic eukaryote originating from different event
Paulinella chromatophora
Accessory pigments
absorb different wavelength of light to chlorophyll, so provide energy to algae in deep water
Kleptoplast
stolen plastid through secondary endosymbiosis
Mixotroph
feed through both predation and photosynthesis eg. Euglena
Secondary endosymbiosis
photosynthetic eukaryote with primary plastids is engulfed
Evidence of secondary endosymbiosis
- plastids have 4 membranes
- in some cases original nucleus of eukaryote is still present reduced form of nucleomorph
- relationships based on plastid DNA show brown seaweed is directly related to red algae
Lost photosynthesis
Once gained, photosynthesis can be lost eg. common in Alveolata
Tertiary endosymbiosis
occurs in lineages where photosynthesis was lost eg. Dinoflagellates
Dinoflagellates
responsible for algal blooms
Emiliana huxleyana
Haptophyte, ocean organism that produces blooms
Effect of E.hux on climate
- increases reflectivity of ocean
- promotes cloud formation my excreting dimethyl sulfoxide
- body made from calcium carbonate, create geological formation
Diatom
photosynthetic organism with silica shell
Plasmodium
malaria causing parasite, recent photosynthetic ancestor, plastids contain genes for survival due to transfer
Green algae
green photosynthetic organisms, daughter cells stay attached through binary fission
Colonial lifestyle
- filamentous or spherical
- all cells are equal
- not usually attached to substrate
- cells can survive alone as metabolically independent
- all cells can have sex
prone to being swept away
Multicellular lifestyle
- cells are not all equal
- cells are specialised
- not all cells are metabolically independent
- usually attached to substrate
reinforced bottom structure, cannot be swept away - simultaneous occupation of multiple environments
- not all calls can have sex
Problems of plants moving to land
- Hydration
- Support
- Water for metabolism
- Nutrient uptake
- Temperature variation
- Damaging light levels
- High oxygen concentration
- Sex cell dispersal
- Dessication of gametes
Advantages of plants moving to land
- No filter on useful light
- High O2 concentration
- Escape competition
- Escape predation
Lichen
producers, association of fungi with single cell algae
- fungus provides structure and inorganic nutrients
- Algae photosynthesises
Haplo-diplont
all land plants, have a sporophyte and gametophyte generation
Early land plants
- spores covered in sporopollenin
- gametes produced in gametangia
- eggs retained on mother plant
- zygote retained and supported by mother plant
- sporophytes dependent on mother
- spores produced in sporangium and released
Apical meristem
responsible for building plant as it grows
Liverwort
- earliest group of land plants
- can be leafy - one cell thick
- can be thalloid - flattened branched stem
Bryophyte
- hornworts, liverworts and mosses
- sporophyte is constantly dependent on gametophyte
Mosses
`- very diverse, found in most places apart from deserts
Sphagnum
Bog moss, ecologically important, occupies and creates peat bogs, makes environment mor acidic and allows peat to form from carbon
Polytrichum
- moss which evolved splash cups for easy fertilisation
- some cups are coloured to attract insect pollinators
Dwarf males
mosses develop ability for male spores to germinate when they land on female
Hornworts
- Anthocerophyta
- look like liverworts
- have stomata
- sphorophytes are long lived and remain dependant on gametophyte
Vascular Plants
- freely dispersed spores germinate to gametophyte
- sporophyte forms and grows nigger and forms roots and branches
- sporophyte becomes independent and mother gametophyte dies
Terminal sporangia
- spore bodies at end of stem
- seed plants, monilophyta
Lateral sporangia
- spore bodies along edge of stem
- lycophyta
Monilophyta
- include ferns
- leaves are megaphyll, evolved through webbing
- evolved from terminal sporangia, spores moved underneth through selection to keep dry
Lycophytes
- inclides microphyll leaves, evolved from scales
- evolved fro lateral sporangia and leaves are simple and triangular
- includes Selaginella
Homosporous
- only one type of spore, bisexual
- no sexual dimorphism
- single type of gametophyte
Heterosporous
- two types of spore, sperm or egg
- allows sexual dimorphism
- unisexual gametophyte
Progymnosperms
- spores remained on mother plant due to dry conditions and grow into gametophyte
- gametophytes are dispersed instead of spores
- male gametophyte lands on female still attached to mother plant
Progymnosperm male gametophyte
- reduced in size
- loss of independence, no chlorophyll
- sculpted for air resistance
- becomes pollen
Progymnosperm female gametophyte
- reduced in size and complexity
- totally dependent on the mother
- becomes enclosed by mother
- becomes ovule
Archaegonium
specialised organ that produces egg cell, exists in early seed plant
Why seeds are beneficial
- headstart in growth
- are supported
- food supply
- protection against animals and dessication
Seed plant
- spores are made through meiosis and retained and supported
- male gametophytes are dispersed and land on femle
- sporophyte grows and seeds are dispersed
- favoured by dry environments
5 lineages of seed plants
Cycadophyta - large, spiky, poisonous (swimming sperm)
Ginkophyta - only one living species, Ginko boloba (swimming sperm)
Coniferophyta - some are deciduous, some are evergreen (pollen tube)
Gnetophyte - Gnetum, Ephedra, Welwitschia (pollen tube)
Anthophyta - Angiosperms
Ancestral Angiosperms
- low density
- used insects or other pollinators
- ovule becomes enclosed
- gametophyte reduces to 7 cells and becomes more adaptable
- pollen sticks out to touch insects
- coloured petals attract insects
- have endosperm
Endosperm
- specialised food tissue from double fertilisation
- pollen has 2 nuclei
- Tube cell works then dies
- Generative nucleus divides into 2
Vascular tissue
Xylem - takes up water
Phloem - takes sugars from leaves to roots, have companion cells with nucleus to improve transport control
Monocot
- one seed leaf
- always monoaparture (one hole)
- 20% of world population
- reffered to as bulbs
- contains bluebells, daffodils, grasses
- became aqutic, became herbaceous, returned to land
Dicot
- two seed leaves
- either monoaparture or triaparture
Apartures
holes in angiosperm pollen in which water enters, allowing pollen to germinate
Archaedicot
- primitive, monoaparture dicots
- 3% of world population
- includes magnolias and water lilies
- usually tropical
- monocots and eudicots evolved independently from these
Eudicot
- advanced, triaparture dicots
- 77% of world population
almost any European tree, apart from conifers
Amborella
- first split between living flowering plants
- happened 175 million years ago
- one living species in Caledonia
Second branching flowering plants
- water lilies
- first known aquatic seed plants
- lots of petals
- first herbaceous seed plants
Third branching flowering plants
contains 3 rare families
Fourth branching flowering plants
- splits into 5 lineages
- Magnolia group
- Monocots
- Eudicots
- 2 other small groups
Magnolia group
- contains magnolia and 97% of archaedicots
- first herbaceous and non-aquatic seed plant
- archaedicots have unique oil cells
Aristolochia
- has specialised pollination: pollination by deception
- fly is attracted to smell of rotting meat, crawls inside, trapped due to downward pointing hairs, pollen scatters over fly body, fly escapes, pollinates other flower
Evidence for monocots becoming herbaceous
- at base of family tree they arose from archaedicots
- many basal monocots are aquatic
Monocot defining characters
- no secondary growth, which fattens tree trunk (only one is tree = palm tree)
- have herbaceous ancestor
- have vascular bundles of complex structure, give wek support, improved flexibility for aquatic ancestor
- absence of primary root (aquatic angiosperms are free floating)
- loss of cotyledon
- leaf ventilation and shape (linear leaf shape appears in aquatic plants)
Eudicot flower specialisation
- earliest flowers had petals in spiral arrangement
- lineages evolved to have whorl arrangement
- whorl arrangements can evolve to bilateral symmetry, fused carpals, or fused petals
Compound flowers
- small flowers group together in the middle, and open at different times to receive different pollen to increase genetic diversity
- large flowers to attract attention
Seed dispersal by animals
- hooks: attach to animal externally
- internal food - eaten and excreted
- external food - taken and stored away
Abiotic seed dispersal
- wind
- physical eg. catapult
- water
Ethnobotany
indigenous uses of plants give clues to undiscovered drugs
Parasitic orchids
- all orchids start off being parasitic on fungi
- seeds germinate if parasitic fungus attempts to attack
- some become entirely photosynthetic, others remain partly parasitic to grow in shade
Parasitic toothwort
- are parasites on trees
- lost ability to make chlorophyll
- steals energy from tree
Parasitic striga
- attacks African maize crops
- seed senses root, germinates and seeks root, atttaches, starts parasitism, aerial parts develop
Solution to striga parasite
- legume Desmodium is planted
- more attractive to striga
- striga senses desmodium root, germinates and seeks root, can’t attach, starves and dies
Carnivorous plants
- either use sticky leaves, or pitfall trap structure
- do not eat insects for energy as they photosynthesise
- eat insects for extra nutrients
Strangling figs
- land and germinate on tree branch, grow doen and develop thickly over trunk, strangle snd kill tree, take its place
Arum
- compound flower (monocot), uses pollination by deception
- smell of rotting meat, attract insects
- beneficial for plants that occur at low frequencies
Ophrys
- “bee orchid” - flowers mimic female insect
- male insects attempt to mate with flower, pollen gets attached, fertilisation occurred when insect attempts to mate with other flower
