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.