3.2 Flashcards
What are the characteristics of Eukaryotes?
Most are larger than bacteria and archaea, have membranous organelles, and a cytoskeleton. DNA is in a nucleus that is surrounded by a membrane. Only eukaryotes can be multicellular
What are membranes for eukaryotes?
Synapomorphy, they all have it
What are the properties of simple multicellular organisms?
Adjacent cells stick together via adhesion molecules. Little to no communication or transfer of resources. Little differentiation, most or all cells retain range of functions including reproduction. Every cell is in contact with external environment.
What do all complex multicellular organisms have?
Cell communication and transfer of materials. Differentiation. 3 dimensional structures resulting in cells not in direct contact with the environment
What happens as multicellular organisms get larger?
They have more interior cells that are not in contact with the environment
What are the two mechanisms that transport materials in multicellular organisms?
Diffusion and osmosis, and bulk transport
What is diffusion?
The random motion of molecules, net movement of areas with higher concentration to lower
What is bulk transport?
Any means by which molecules move through organisms at rates faster than diffusion
When is diffusion effective?
Small distances
Why are some plants that use diffusion small?
Diffusion limits the size and shape of organisms so that they can stay in close contact with the environment
True or false: There are organisms that have the cells that require resources near their exterior but have larger interior made up of inactive tissue
True, they do exist
What happened as complex organism became larger?
Evolution of specialized transport systems for bulk transport enabled the movement of molecules faster across larger distances unlike diffusion
How many times did complex multicellularity evolve in eukaryotic groups?
6 times
What are the groups where complex multicellularity evolved?
Animals, Green algae that are ancestors of land plants, red algae, brown algae, and fungi twice
Which 3 groups have complex multicellularity?
Fungi, land plants, and animals
What are protist?
Other eukaryote groups with complex multicellularity scattered among the remaining taxa
What are two characteristics of protists?
Can be single celled, or have simple/complex multicellularity. All live in some kind of watery environment
What are some photosynthetic protist?
Algae
Which algae groups gave ride to land plants?
Green algae
What distinguishes all land plants from green algae?
Evolution of water-proof cuticle and pores/stomata. Fertilized egg develops into a multicellular embryo which attached to parents and is protected by them and nourished
What does a cuticle do?
Prevents water loss from organism
What do pores/stomata do?
Allow gas exchange in photosynthetic tissue
What are the benefits to living on land?
More space, sunlight, and CO2 for photosynthesis
What are the four major transformations in LIFE CYCLE and STRUCTURE characterize the evolutionary history of plants?
The evolution of alternation of generations
The evolution of vascular plants
The evolution of pollen and seeds
The evolution of the flowers and fruits
What is the first major transformation?
Alternation of generations
What two forms do every plant species alternate between?
Haploid gametophyte generation that makes gametes, a diploid sporophyte generation that makes spores
How does alternation of generation benefit plants?
Plants can shift between forms that increase variability and are specialized for fertilization, and forms that increase production and are specialized for dispersal
What must happen with the gametes from the haploid gametophyte generation?
They must recombine to form new individuals which leads to variability
Where did gametophyte evolve and why?
Low to the ground, it can release swimming sperm into the surface layer enhancing fertilization
What do the diploid sporophyte generation produce and with what phase?
Different spores by meiosis
Why is it important to make different spores from diploid sporophyte generations?
The spores disperse through the air and give plants and advantage in colonizing
Where do sporophyte evolve and why?
Taller than gametophyte to produce spores at tip that can easily be carried by the air to different locations
How are light nutrients water and CO2 challenges on land?
The resources are in different locations.
Where do land plants get water and soil nutrients?
Below the ground
Where do land plants get light and CO2?
Above ground
Where do land plants get oxygen?
Above and below ground
What are the risks for plant cells above ground?
They risk desiccation (drying out)
What are the risks for plant cells below ground?
Need food from photosynthesis
What does every land plant have to limit water loss?
A cuticle
What are bryophytes?
plants that rely solely on diffusion to absorb water.
What are properties of bryophytes?
They must remain small and can absorb only surface water. Their cuticle layer is thin, they grow on any wet surface, and they dry out easily
What strategy do bryophytes use to survive on land?
Desiccation tolerance
What is desiccation tolerance?
Can survive extreme dehydration during dry conditions and recover when conditions are suitable
What is the second major transformation?
The evolution of vascular tissue
___ plants evolved ___ and ___ as a strategy to avoid ___
Vascular, roots and vascular tissue, desiccation
Why are roots important to avoid desiccation?
They pull water from the ground, which means they do not need to grow on wet surfaces
What causes the thick cuticles in vascular plants?
The above ground tissue does not need to absorb water, so they have a thick cuticle to prevent drying out
What forms the bulk transport system?
Vascular tissue
What is a bulk transport mechanism?
They can move water and nutrients faster than diffusion over the longer distances.
Which mechanism prevents dryness and how?
The BTM, they move water from non-photosynthetic parts to photosynthetic parts.
What is vascular tissue made up of in plants?
Xylem and Phloem
What does Cohesion-Tension-Transpiration in xylem do?
Moves water and minerals from tissues with access to water (roots) to tissues without access to water (shoot system above ground)
What does the Translocation in phloem do?
Moves sugars from photosynthetic tissues with access to sunlight (Leaves and or stem) to non-photosynthetic tissues (roots, buds, and reproductive systems
What is the only way gas can move through plants?
Diffusion
What physical benefit does xylem tissue provide?
Rigid support for growing upright on land
Why did Xylem evolve?
Early land plants competed for sunlight and space, xylem tissue allowed for more sunlight and space
What does lignin do?
Provide structural support
What are the solutions to prevent spores and gametes from dying?
Selection favored desiccation-resistant spores with thick walls of sporopollenin produced in sporangia.
Gametes were produced in complex, multicellular structures gametangia.
What are the solutions to avoid gametes from not getting enough resources?
Plant embryos are retained and receive protection and nourishment from parent
What is the third major transformation?
The evolution of pollen and seeds
What disadvantages occurred before pollen?
More independence for surface water, need surface water to fertilization, sperm needed to swim to the egg over a short distance.
What are pollen grains?
Tiny male gametophytes that are covered with a tough waterproof layer. They produce sperm
What does the tube cell nucleus do?
Guides the pollen tube
What does the generative cell do?
Divides to form two sperm
How are pollen grains carried?
Wind or animals
What happens once the pollen arrives to the egg?
They produce sperm and a pollen tube to transfer sperm to the egg.
What happened when pollen evolved?
Plants did not require water for fertilization and could fertilize from far distances
What did the evolution of pollen and seeds lead to?
Greater independence from surface water
Why was water needed before seeds evolved?
To prevent embryos from drying out
What does a seed consist of?
The sporophyte embryo and a store of nutritive tissue, surrounded by a tough protective layer
How long can seeds survive outside of parent plant?
A long time, 2000 years even
What was the fourth major transformation?
The evolution of the flowers and fruits
How was pollen dispersed before flowers and fruits?
Through the wind
What three things can flowers do?
Protect the female gametophyte, collect or disperse pollen, and attract pollinators
What are synapomorphies in land plants to resist desiccation?
Cuticle and pores
What is the phylogenetic order of red algae to angiosperms?
Red algae, Green algae, nonvascular plants, seedless vascular plants, gymnosperms, and angiosperms.
What are synapomorphies in land plants related to reproduction?
Complex gametangia, Thick-walled spores, Embryos retained in parent plant, Alternation of generations
What are the three land plant groups categorized by reproduction and vascular tissue?
Nonvascular plants (Bryophytes and others), Seedless (spore dispersing) vascular plants, and Seed plants
Which plants have gametophyte dominated life-cycles?
Non-vascular plants
Which life cycle evolved later?
Sporophyte dominated cycles
How long is the gametophyte stage in vascular plants?
small and short lived
What are seed plants defined by?
Production of seeds and pollen grains
The seed plants are a __phyletic group that consist of the ___ and the ____
Monophyletic, gymnosperms, angiosperms
What stage are the gymnosperms and angiosperms in?
sporophyte stage
How large is the gametophyte stage?
Small, they retain their spores
What two kinds of spores do seeds plant produce to develop into gametophytes?
Male and Female
What are gymnosperms?
Non-flowering seed plants
What properties do most gymnosperm seeds contain?
Seeds are either exposed or partially exposed to the environment. They usually develop in dry or fleshy cones
What are angiosperms?
Seed plants that produce flowers or fruits
How do angiosperm seeds develop?
Completely enclosed inside the ovaries of the flower, later to become fruits that enclose seeds
