Plants

plants dominate most of the land on Earth plants and plant products are all around us, in the

products we use and the foods we eat

Classification

evolved from charophytes, a group of green algae (belong to the kingdom Protista)

Classification Cont’d… plants are classified into four major groups: (1)

bryophytes, (2) pteridophystes, (3) gymnosperms & (4) angiosperms

Characteristics (almost) all plants…

are multicellular eukaryotic organisms photosynthesize have cell walls made of cellulose are sessile (don’t move from place to place)

yet plants are very diverse

Life Cycle plants have an alternation of

generations life cycle a plant in the diploid stage is called

a sporophyte sporophyte’s diploid cells divide by

meiosis to produce haploid cells which form asexual spores

the spores grow into gametophyte individuals

gametophytes mature and produce haploid sex cells (gametes)

gametes undergo fertilization to form diploid zygotes

zygotes grow into sporophyte individuals, and the cycle continues

Early Adaptations for Life on Land most plant species living today live on the land but primitive

ancestors of today’s plants, however, lived in the water To adapt to land plants developed…

cuticles: waterproof, waxy coating made by the epidermis of plants to prevent water loss

stomata: small openings in the epidermis of a plant that can open and close to allow gas exchange

Bryophytes bryophytes are the simplest of

land plants and include the mosses, liverworts,and hornworts

have a protective cuticle and stomata but they do not have specialized vascular tissue or true leaves, roots, or seeds

only grow a few centimetres in height

depend on water (dew or rain)to carry sperm to ovum for reproduction and only the gametophyte is photosynthetic

Life Cycle of a Moss

Lycophytes and Pterophytes

the next major adaptation by land plants was the development of vascular tissue

vascular tissue consists of xylem and phloem which transports water and nutrients

plants with vascular tissue can grow to great heights and access more sunlight

lignin is a very strong component of vascular tissue that makes cell walls more rigid

Lycophytes and Pterophytes Cont’d… lycophytes (club mosses) and

pterophytes (ferns) are seedless vascular plants with large simple roots and stems

many have developed symbiotic mycorrhizal relationships that help them obtain water and other nutrients from the soil

similar to bryophytes, reproduce sexually using sperm and eggs but the sporophytes are photosynthetic and much larger than the gametophytes

Life Cycle of a Fern

the entire male gametophyte is carried from one plant to another by the wind or by animals, instead of travelling through water

not restricted to reproduction over short distances in wet conditions

are the dominant land plants on Earth

Gymnosperms and Angiosperms: The Seed Plants

pollen grains are waterproof capsules that contain haploid male gametophytes

pollination occurs when the male gamete in a pollen grain penetrates an ovule containing a female gametophyte

male gamete fertilizes egg, producing a diploid zygote, or embryo, which becomes a seed

Gymnosperms and Angiosperms: The Seed Plants Cont’d…

Gymnosperms and Angiosperms: The Seed Plants Cont’d… the food supply in the seed

gives the embryo nutrients to grow a small root, stem, and leaves before it can photosynthesize

food supply is a concentrated mix of starch, plant oils, and some protein

seeds are a VERY important food source for many animals

Gymnosperms: The Conifers

gymnosperms include the coniferous trees and other less well known groups of plants

cones are the reproductive structures of conifers

male cones produce and release pollen, and female cones produce eggs

when an egg is successfully pollinated and fertilized within a female cone, an embryo develops within a seed in the cone

many of these are woody trees, and most have needle- or scale-like leaves

narrow leaves and thick cuticles are adaptations that help the trees reduce water loss

Gymnosperms: The Conifers Cont’d…

Gymnosperms: The Conifers Cont’d…

gymnosperms have large, shallow root systems that form a mycorrhizal relationship with symbiotic fungi

Angiosperms: The Flowering Plants

more than 90% of all modern plant species are angiosperms

angiosperms: flowering plants

Angiosperms: The Flowering Plants

flowers: reproductive structures that produce both pollen and eggs

in female flower parts, the eggs are protected in an enclosed ovary

Angiosperms: The Flowering Plants

after fertilization, seeds form within the ovary and the outer tissues of the ovary become a fruit

main function of the fruit is to disperse the seeds

gizmo

Angiosperms: The Flowering Plants the development of flowers and fruits is key to

the success of the angiosperms flowers are specialized for the way the plant is

pollinated (ex. flowering plants that depend on animals for pollination are colorful, fragrant and have nectar)

Angiosperms: The Flowering Plants each fruit is adapted to protect and disperse the

seeds within it using wind, water, and other organisms (ex. burdock fruit has needles that stick to animals)

Homework

answer 3.2 questions # 2-7