Classification of Plants - Sciencepoint...
Transcript of Classification of Plants - Sciencepoint...
Classification of Plants
Plants
Aquatic Plants
• Ex. green algae
Similarities between green algae and land plants:
• A) have chlorophylls a and b
• B) cellulose cell walls
• C) store food energy in the form of starch (rather than glycogen)
Plants to Land (400MYA)
Adaptations that needed to be evolved before plants could live on land:
• A) protection from drying out
• B) system of transport from outside environment to cells in the body of plant
• C) system to support the body of plant
Adaptation to Land
3 organs that developed to adapt to life on land:
• A) roots: penetrate soil to anchor plant; reach water source
• B) leaves: greater surface area for photosynthesis
• C) stems: rigid tissue to raise and support leaves
Land plants: non-vascular vs. vascular
Vascular plants appeared 360MYA
A vascular tissue :
• a system of tubes that carry water and dissolved nutrients through a plant
Land plants: non-vascular vs. vascular
Non-vascular (bryophytes)
• No vascular (transport) tissue
• Have root-like, stem-like and leaf-like structures (poorly developed roots, leaves and stems)
• Grow short, small
• ex. mosses, liverworts, hornworts
Vascular (tracheophytes)
• has vascular tissue to transport water and nutrients
• Have true roots, stems and leaves
• Grow taller, larger
• 1) seedless (spore producing)
• Ex. ferns
• 2) seed producing
• Ex. conifers, flowering plants
Non-Vascular vs. Vascular
Advantage of vascular plants?
• - can live in drier environment
• - can grow larger (water and nutrients can reach far with the vascular tissue)
Non-vascular plants live in moist environment and have smaller sizes.
Non-vascular (bryophytes)
Mosses Liverworts
• Hornworts
Vascular (tracheophytes) 1) Seedless (spore-producing) ex. ferns
• Grow in marshes and edges of shores; requires water for reproduction – spores (sperm) swim in water to the female organ (in different plant or same plant)
Advantages of having seeds
• A) food storage
• B) tough waterproof coat – protection against harsh conditions
• C) remain dormant- survive exposure to harsh conditions
• D) sexual reproduction without needing water
Gymnosperm- “naked seed” ex. ginkgoes, conifers
Angiosperms-flowering plants
Examples Gymnosperms vs. Angiosperms
• Conifers: produce cones in the spring and summer
• Male vs. female cones
(in clusters) (scattered, hidden seeds)
• Flowering plants
• Also grass and herbs
Seed Structure Gymnosperms vs. Angiosperms
• Means “naked seed”
• Seeds that are exposed to the environment (often as cones)
• Thin cover of protection
• Means “seed in a vessel”
• Seed = embryo +nutrient storage+ coat
• Seeds that are not exposed to the environment (drought, fire…)
• Seed protected with body of fruit
Preferred Environment Gymnosperms vs. Angiosperms
• Environments with long, cold winters and low amounts of nutrients in the soil
• Found in Canada and northern Europe and northern Asia
• Found all over the world
Number of species Gymnosperms vs. Angiosperms
• Smaller in number
• Approx. 1000 species
• Larger in number
• Approx. 250 000 species
. 2 groups
Monocotyledons Dicotyledons
Flowering
Plants
(Angiosperms)
. roots, stems, leaves
. vascular tissues (transport)
. flowers, fruits (contain seeds)
Two peanut seeds Two apple seeds in the hard ovary vs in the fleshy fruit
Monocotyledons and Dicotyledons
Cotyledon: the structure in a plant’s seed that stores carbohydrates for the seedling
• It’s known as “seed leaf” because the plant’s first leaf develops from it.
• ex) onion- single leaf monocot
• alfalfa- two leaves dicot
Monocotyledons
Parallel veins
Dicotyledons
Veins in network
Structure Monocots Dicots
Number of cotyledons
1 2
Number of flower petals
Multiples of 3 Multiples of 4 or 5
Number of species
Fewer More
Examples Tulip, lily, corn, onion, grass, rice, banana
Rose, maple tree, carrot, potatoes, beans
Root structure
Structure Monocots Dicots
Root cross-section
Vascular bundles are arranged in a ring
xylem in the center of the root (with an X shape) and phloem
outside the xylem.
Root system Fibrous roots- many thin roots
Tap roots – one large vertical root with smaller branches
Stem cross-section
Vascular bundles are scattered
Vascular bundles are arranged in a ring
Tissue Herbaceous –soft & flesh stems
Only about 10% are woody
Woody- tough, rigid
Monocot Stem vs. Dicot Stem vascular bundles- scattered vs. in a ring
Leaf
Structure Monocots Dicots
Leaf cross-section
Spongy mesophyll
Palisade mesophyll + spongy mesophyll
Leaf structure Long strips
Parallel veins
Broad leaf
Net-like veins
Double fertilization
• 1) between a sperm(1n) and the egg (1n) becomes the zygote (2n)develops into an embryo
• 2) between a sperm(1n) and the two polar nuclei (n +n) becomes the endosperm (3n) provides nutrients for the embryo
• each ovule forms a seed (there are many ovules in the ovary)
• the ovary develops into a fruit
Gametes
• Inside the anther, microspores are produced through meiosis. These microspores give rise to the pollen grain (1n).
• The female reproductive organ, the ovary, contains developing ovules. Each ovule produces megaspores (haploid) through meiosis. One megaspore survives in each ovule and develops into an egg (1n).
• When pollen reaches the stigma, it grows a pollen tube to extend down the style.