Plants Flashcards
What is biodiversity?
The variety of life, in all its manifestations. It encompasses all forms, levels and combinations of natural variation.
How much biomass - excluding microbes - do plants represent?
90%
What do Plants provide for humans?
Feed us, provide drugs, materials for clothing and building, one of our main sources of fuel - living and dead
For how much of Earths history was the land face largely lifeless?
3000my
When did plants begin to colonise land?
500mya
When did plants evolve to grow tall, leading to the first forests?
370mya
How many known plant species are there?
> 290 000
How do plants enable other forms to exist successfully on land?
Roots provide habitats by anchoring the soil, supply oxygen and provide food for terrestrial
What key characterises are shared by plants and protists?
multicellular eukaryotes, photosynthetic autotrophs
What else, other than plants have cell walls made of cellulose?
Green algae - charophytes and dinoflagellates
What are charophytes?
Division of freshwater green algae, possibly closest relative to land plants.
What similarities to charophytes and green algae share?
Rosette shaped cellulose, Peroxisome enzymes, Formation of phragmoplast, Structure of flagellated sperm
How are protein arrays arranged in non charophyte algae?
Linear
Describe what is meant by Rosette shaped cellulose
Cells have circular petal shaped arrays of protein on the plasma membrane, which synthesise cellulose microfibrils
What is the phragomplast?
Mechanism in plant and charophyte cell division, forms during late cytokinesis, a group of microtubules that form between the dividing nuclei acts as a scaffold for forming cell plate
Where do charophytes live?
shallow waters at the edge of ponds and lakes
How did natural selection in the habitat of charophytes lead to the evolution of land plats?
Live in habitats that may dry out, so selection favours plants that can withstand long periods out of the water.
What feature do charophytes have to protect their zygote when dry?
Strong sporopollenin walls
What are the benefits of moving onto land?
Bright, unfiltered sunlight, more plentiful CO2, soil rich in minerals and nutrients, relatively few herbivores
What were the physiological problems did plants have to overcome moving onto land?
Water balance, Availability of essential nutrients and gases, Support, UV protection, reproductive strategy
How did plants adapt to limited water availability on land?
No longer bathed in water, had to use rhizoids/Roots, xylem, cuticle and stomata
How did plants adapt to obtain nutrients and gases on land?
Collect from soil and atmosphere using roots and stomata
How did plants adapt to support on land?
use lignified conducting tissues
How did plants adapt to UV protection on land?
use of a cuticle
How did plants adapt their reproductive strategy for life on land?
protected by sporopollenin, dispersal by new vectors
What are the derived traits shared by plants?
Alternation of generations and multicellular dependent embryo
Walled spores produced in Sporangia
Multicellular Gametangia
Apical Meristems
What is alteration of generations?
Lifecycle alternates between multicellular haploid organisms and multicellular haploid organisms, each generation gives rise to the other
What is the diploid generation called?
Sporophytes
What is the haploid generation called?
Gametophyte
Why was the haploid stage named gametophyte?
Named because it is the gamete producing plant, production of haploid gametes by mitosis.
How is the diploid sporophyte formed?
Fertilisation of haploid gametes, diploid zygote is created, mitotic division of zygote leads to new sporophyte plant
Why is the diploid stage named sporophyte?
Meiosis is a mature sporophyte produces haploid spores, that can develop into a new haploid organism with mitosis
Where do multicellular embryos develop?
In the tissues of female gametophyte, from zygotes. The parent tissue provides nutrients via special placental transfer cells
What are plant spores?
Haploid reproductive cells that can grow into multicellular haploid gametophytes
What polymer makes walls of spore tough and resistant?
Sporopollenin
What does sporopollenin allow plants to do?
Disperse spores through dry air without harm
Where are spores produced?
On the sporophyte, in multicellular organs called sporangia
How are spores made in the sporangia?
Diploid cells called sporocytes undergo meiosis and generate haploid spores
What are the differences in the way charophytes and sporophyte produce their pores?
No multicellular sporangia in charophytes, and their spores lack sporopollenin
Where are the gametes in plants produce?
Gametangia
What are the female gamentangia called?
Archegonia
Describe the archegonia
Pear shaped organs that produce a single non motile egg, retained in the bulbous part of the organ.
What are male gametangia called?
Antheridia
Describe the antheridia
Produce sperm and release them into the environment.
How does the sperm reach the eggs in many modern day plants?
Have flagella and swim to the eggs through water droplets.
What are the essential resources plants have to gain from their surroundings?
Co2, Light, Water, minerals and nutrients
What are apical meristems?
Localised regions of cell division at the tips of roots and shoots.
What are secondary compounds?
products of secondary metabolic pathways
What are the secondary products in plants?
alkaloids, tamarins, Flavinoids
What are non vascular plants called?
Bryophytes
What are vascular plants Called?
Tracheophytes
What are the distinguishing features of bryophytes?
Conducting tissues not lignified, gametophyte dominant with sporophyte subsidiary.
What are the distinguishing features of sporophytes?
Conducting tissues lignified, sporophyte dominant, with gametophyte subsidiary.
What is the plant kingdom known as?
Embryophta
What are the three classes in the division Bryophyta?
Hepatics - Liverworts, Musci - mosses, Anthocerotes - Hornworts
What are the throw classes of tracheophytes?
Pteridophytes, Gymnosperms, Angiosperms
What are the orders of pteridophytes?
Lycopsids, Spenopsids, Ferns
What are the orders of Gymnosperms?
Cycads, conifers, conifers, ginkgos, genetales
