Charophytes Green algae closest to plants

Plant Diversity

Plant Evolution Evolution of structures for better survival on land Bryophytes – mosses Seedless Vascular Plants – ferns Gymnosperms – conifers Angioserms – flowering plants

Bryophytes Examples of bryophytes are mosses No vascular tissue Must remain moist to survive Waxy cuticle to prevent dehydration No lignin – they do not stand tall, but cover the ground like a mat

Reproduction Review Gametes – sperm (pollen) and egg Gametes have half the chromosome number which we call being haploid Gametes become haploid through a process called meiosis. Normal body cells are called somatic cells. These are all of the other cells of the plant EXCEPT gametes. Somatic cells are diploid, which means they have the total number of chromosomes. A spore is NOT a gamete. Spores can grow into a whole organism, gametes must fuse together to form a zygote.

Bryophyte Reproduction In mosses, there are two parts of the body Gametophyte – soft, green, sponge-like portion of the moss Sporophyte – stalk growing out of the gametophyte

Bryophyte Life Cycle

Life cycle Start with male and female haploid (n) gametophytes. Antheridium contain the sperm – at the tip of the leaf Archegonium contain the egg – at the base of the leaf Fertilization occurs via water transport – diploid (2n) zygote is formed and grows into a mature sporophyte Spores undergo meiosis and are now haploid (n). Spores fall to the ground and bud new male and female haploid (n) gametophytes.

Ferns

Ferns Ferns have vascular tissue – next level of adaptation However, their sperm still swim like mosses 12,000 different species Found in the tropics and temperate forests Date back to 360 MYA – carboniferous period The remains of these plants create peat and through the years heat and pressure turn the peat into coal. Coal is a fossil fuel used to generate much of our electricity. The most extensive coal beds are from the carboniferous period.

Fern Life Cycle

Fern Reproduction Sorus on the underside of the leaf hold spores Spores germinate into haploid gametophyte Antheridium holds the sperm and archegonium holds the egg. Fertilization occurs through water New diploid sporophyte begins to grow.

Gymnosperms

Gymnosperms Near the end of the Carboniferous period, the climate became cool and dry. Lots of ferns and mosses began to die Gymnosperms become very successful because of seed production Conifers are the most diverse gymnosperms – pines, spruces, firs, and redwoods Thick cuticle on the leaves, stomata in pits to prevent water loss Reduction of gametophye, pollen in cases, and seeds are also adaptations to life on land.

Pine Cones

Gymnosperm Reproduction

Gymnosperm Reproduction Male pollen - microspore undergo meiosis (n) Megaspore mother cell is in the pine cone and undergoes meiosis (n) Pollen fertilizes egg in the archegonium Creates embryo which is the young sporophyte (2n). Sporophyte grows into mature tree.

Coniferous Forests 190 million acres are designated national forest Loss of forests due to grazing, lumber industry, mining, and public recreation.

Conifers of Yosemite

Incense Cedar

Angiosperms Flowering plants Dominate most of the Earth 250,000 species Wheat, corn, oats, barley Citrus, fruit, vegetables Cotton, flax Cherry and walnut furniture Vascular adaptations make it easier for angiosperms to live on land Flowers are why they are so successful.

Structure of a flower A flower is composed of four whorls Sepals – green parts that enclose the flower before it opens Petals – attractive part of the plant that attracts birds and bees Stamen – anther and filament Carpel – stigma, style and ovary

Angiosperm Life Cycle

Angiosperm Life cycle Mature sporophyte (2n) contains pollen and egg. Pollen and egg undergo meiosis and become haploid (n). Pollen is released and carried to the stigma (sticky) 2 Pollen travels down the style to the ovary. Double fertilization occurs creating a zygote and endosperm Endosperm is the food for the growing diploid embryo (2n).

Fruit Now the ovary is called the fruit and the ovule is called the seed. The seed will grow into a new mature sporophyte (2n).

Examples of seed dispersal

Medicines derived from plants

CAM plants Succulents – pineapple, cacti, jade plant CAM plants open their stomata only at night to let CO2 in and O2 out. CO2 is packaged in a 4-Carbon compound and released to calvin cycle during the day. Only open the stomata at night to prevent water loss.

Jade Plant