Lecture 17 Flashcards
What are 3 reasons that green plants are important? and what are some direct needs to humans?
- key photosynthesizers (consume CO2 and produce O2) and produce carbohydrates
- energetic basis for all terrestrial ecosystems (support all the energy needs for the diversity of animal life)
- support “ecosystem services”, like soil production, nutrient recycling, soil stability, atmosphere composition, local weather and climate, surface water flow etc.
needs: food, building material, fuel, fibres, pharmaceuticals, aesthetics
What are the 3 major groups of “algae” defined by pigments: and considered to be POLYMORPHIC clades (different ancestors)
Brown algae (many seaweeds like kelp)
Red algae
Not algae : the “blue-green algae” should be called CYANOBACTERIA
What does polymorphic mean?
The occurrence of more than one form, as several alleles of a particular gene or winged and wingless forms of the same species
where do most GREEN algae live?
- most live only in aquatic or other wet environments
What are the 4 things that need to be supported during the transition to land?
- desiccation protection : the ability of an organism to withstand or endure extreme dryness, or drought-like condition
- support (growing tall)
- gas exchange and transport
- reproduction? easy in water: reproductive cells can swim freely
What are some synapomorphies with aquatic green algae and terrestrial plants?
characteristics of chloroplasts (photosynthetic organelles)
- photosynthetic pigments in both include chlorophyll a & b and carotene!
- thylakoids (stacked membranes) in plant chloroplasts are similar to green algae in structure
- synthesize starch as a storage product
plants adapted to life on land through what?
natural selection!
ex. new mutations: waxy surfaces (cuticle) would reduce drying
explain a basic synapomorphy of land plants?
waxy cuticle and stomata (pores)
- waxy cuticle minimizes water loss through the surface cells
- stomata can open and close to allow gas exchange while minimizing H2O loss
What is the def of green plant?
- multicellular eukaryotes that are photoautotrophic; a monophyletic group that includes green algae, non-vascular plants, vascular and seed plants
- produces starch
- carbon from CO2
- hydrogen and oxygen from H2O
What does photoautotrophic mean?
organisms that can make their own energy using light and carbon dioxide via the process of photosynthesis
What are the 3 basic type of land plants and explain them a little
- nonvascular plants: do not have vascular tissue to conduct water and provide support (ex. mosses)
- have vascular tissue but do not make seeds (ex. ferns)
- have vascular tissue and make seeds (ex. flowering plants or angiosperms and gymnosperms)
review the 5 major intervals of the fossil record of land plants
- origin of land plants : first evidence of land plants: cuticle, spores, sporangia
- Silurian-Devonian explosion: most major morphological innovations: stomata, vascular tissue roots, leaves
- Carboniferous: club mosses and horsetails abundant: extensive coal-forming swamps
- gymnosperms become increasingly abundant: both wet and dry environments blanketed with green plants for the first time
- Angiosperms abundant : diversification of flowing plants
at what period did the intial colonization of the land by small, simple plants began the transformation of Earth to a “green planet”?
- Ordovician (before Silurian where new adaptations were well developed)
- diversification of taxa, and increasing size continued during the Silurian-Devonian “explosion”
What happened in the Silurian Period?
- improved adaptations to land (small plants) with cuticle, stomata, support tissues, spores
What happened during the Devonian Period?
- first trees
- first seeds
- first insects
- first tetrapods
- also called the “Age of Fishes” with high diversity in salt and fresh water
How can vascular plants grow to tree size?
- due to conduction and support tissues
-
What’s the synapomorphy of vascular tissues (xylem and phloem)?
- VTallows for efficient transport of water and minerals (xylem) and sugars (phloem)
- xylem tissues contains LIGNIN which is a tough chemical that provides hard structural support
- VT allows for true stems, roots and leaves
why is wood hard? due to what tough chemical?
- LIGNIN
What is the primary wall of plants made of? the secondary wall?
- primary : cellulose
- secondary : lignin
What hardens plant tissues?
- VT (xylem) and lignin
What are the 3 selective advantages for improved traits of the plants (growing taller in the Devonian)?
- increased support and reduced height constraints: grow taller and compete for light. PHOTOSYNTHETIC COMPETITION
- better anchoring (hard roots) and increased access to water and nutrients
- increased surface area (leaves), photosynthetic capacity, and biomass
explain the land plant life cycle
- a multicellular haploid GAMETOPHYTE alternates with a multicellular diploid SPOROPHYTE
ADD THE LIFE CYCLE FORM THE BISC LAB MANUAL
- spores-mitosis-gametophyte-mitosis-gametes-fertilization-zygote-mitosis-sporophyte-meiosis
What do sporophytes produce and how?
- spores are produced by meiosis in the sporangia
-
What are the spores in land plants protected by?
- outer coat made of sporopollenin, complex waxy polymer that resists drying
- the inner cells can be dispersed widely and start growing into a gametophyte in proper environments
What do gametophytes produce and how?
- gametes
- eggs and sperms are produced through mitosis
which part of the gametophyte produces sperm and which part produces the egg cells?
- Antheridia produces sperm that needs water to reach eggs on another gametophyte
- Archeogonia produces egg cells
Whats the 3rd part of a gametophyte?
- rhizoids
explain the fern life cycle
- sporophyte dominant
spores (dispersed by wind) - mitosis - developing gametophyte - mitosis - mature gametophyte - sperm swims to egg - fertilization - zygote (in the archegonium) - sporophyte - mitosis - mature sporophyte - meiosis - spores
What happened from Devonian to Carboniferous “coal age”
- seedless vascular plants
- constraint: moist environments, flagellated sperm needs film of water to swim to egg
- giant insects!
Which 2 plants were gametophyte dominant
- mosses and liverworts
Why were there giant insects in the Carboniferous Period?
The high oxygen condition of the mid-Carboniferous period and the humid conditions allowed insects to grow very big on land
- diffusion into insects allowed larger size
What is pollen?
- a male gametophyte protected by a spore coat made of sporopollenin
- the male gametophyte produces sperm to fertilize ovules (eggs) produced by a female gametophyte
- male gametophytes can travel by wind or animal, and are NOT DEPENDENT ON A FILM OF WATER
What is the consequence of seeds and pollen combined?
- freed seed plants form reproducing in moist environments
- allowed for dispersal
- colonization of most land surfaces
- allowed interruption (dormancy) in their life cycle
What are the 2 major groups of seed plants
- gymnosperms and angiosperms
what are gymnosperms
- naked seed plants
- include all the living seed plants that are not angiosperms
- constraint: wind-pollinated and so are dependent on high pollen production and wind dispersal (random) for pollination
What are angiosperms?
- flowering plants
- can use both wind, but especially transfer of pollen by pollinators!
Where are the seeds usually formed in gymnosperms?
- mostly formed on the surfaces of cone scales, and can be scattered when the cones dry out and open, or scatter
describe the pine life cycle
microspore forms pollen grain - mitosis - pollen grain (male gametophyte) - pollination via wind - pollen grain meets the fertilization area - pollen tube delivers sperm to egg - fertilization/mitosis - embryo - seeds disperse via wind or animals - developing sporophyte - mature sporophyte
2 diff pathes
- cones with microsporangia
- ovulate cone - ovules - megasporangium - meiosis and back to pollen grain meeting the fertilization area
What is the consequence of lowers and vector pollination (not just wind)
- insect-pollinated plants are not dependent on the wind and produce much less pollen
- live at much lower densities, since pollinators come to them. this enhances biodiversity through specialization and speciation
how does a fruit help a seed?
- protects it and aid in the dispersal by animals, wind or water
- the fruits of angiosperms surround and protect the seeds inside the fruits
explain the angiosperm life cycle
microspore - mitosis - pollen grain - pollination - meets egg at the bottom of carpel (megasporangium - meiosis - megaspore - mitosis - female gametophyte) - double fertilization (unique to angiosperms) - zygote - mitosis - seed - developing sporophyte - mature sporophyte - top of stamen - meiosis - microspore
What is the carpel?
- ovary with ovules (eggs)
