Botany Unit NotesBotany Unit NotesPart I

What is a Plant?What is a Plant?When you are asked,

“what color is life?”, the color that comes to mind is usually green!

It is no wonder that all of Earth’s living systems ultimately depend upon plants

What is a Plant?What is a Plant?Plants are multicellular eukaryotes

that have cell walls made of celluloseMany plants undergo photosynthesisPlants include: trees, shrubs, and grasses

Also ferns and mossesMost are autotrophs except for a few

parasitic plants and saprobesSaprobes feed on decaying organic material

What Plants Need to SurviveWhat Plants Need to Survive

Sunlight ~ plants use the energy from the sun to carry out photosynthesis

Water and Minerals ~ all cells require water and it is used during photosynthesis plants absorb minerals from the soil needed for plant growth

What Plants Need to SurviveWhat Plants Need to Survive

Gas Exchange ~ plants need Carbon Dioxide and even Oxygen to carry out photosynthesis

Movement of Water and Nutrients: The water and minerals taken up by the roots of plants needs to be transported to the structures that carry out photosynthesisThese are hundreds of feet in the air

sometimes!

The Origin of PlantsThe Origin of Plants

It all started in the waterSome scientists believe

that the first plants came from ancient, photosynthetic prokaryotes

The oldest known fossils of plants show them to be around 500 Million years old

Green Algae

The Origin of PlantsThe Origin of Plants

Overview of the Plant KingdomOverview of the Plant Kingdom

Botanists divide the Plant Kingdom into 4 groups based upon three features: Water-conducting tissues Seeds Flowers

The Four Groups Cone bearing ~ 760 species Ferns & their relatives ~ 11,000 species Mosses & their relatives ~ 15,600 species Flowering plants ~ 235,000 species

The most abundant plants of today are the flowering plants making up 90% of all plants on Earth

Overview of the Plant KingdomOverview of the Plant Kingdom

Evolution of Land PlantsEvolution of Land Plants

As plants evolved they obtained important traits: Non-vascular tissues (primitive)

Early plants that needed to be near water to diffuse it into their cells (bryophytes: mosses, liverworts, hornworts)

Vascular plants (seedless came first) Plants that have specialized tissues capable of drawing

water up from the soil through roots (Ferns & horsetails) Seed producing plants

Plants able to protect their young in a durable seed (Gymnosperms: Cycads, Gnetophytes, Conifers, etc)

Seeds enclosed in fruits (advanced) Plants that adapted an attractive fruit to have animals

disperse their young (Angiosperms: Grasses, fruit trees, shrubs, etc)

Seedless Vascular PlantsSeedless Vascular Plants

The first seedless vascular plants arrived on land around 420 million years ago

The new adaptation of transporting water and nutrients through the plant using vascular tissue allowed them to grow much taller than the mosses and other bryophytes

Vascular TissuesVascular Tissues

Vascular tissues allowed plants to grow taller & transport water and nutrients

Xylem moves water up the plant from the roots

Phloem transports sugars and nutrients of photosynthesis down through the plant

Seedless Vascular PlantsSeedless Vascular Plants

This group contains the club mosses, horsetails, and ferns

What makes them different from the earlier plants is that they have true roots, stems, and leavesClub Mosses – Phylum Lycophyta, millions of years ago they existed as tall plants towering over 100 ft!

Today they are small plants living in moist woodlands

Seedless Vascular PlantsSeedless Vascular Plants

Horsetail – Phylum ArthrophytaThe only living species left of this

phylumAll plants in this Phylum belong to

the Genus Equisetum and has true roots, leaves, and stems

They reproduce by way of spores released from specialized structures

They look like tall grasses and are found near water most often

They are popular pond plants and used for decoration in Asian gardens

Seedless Vascular PlantsSeedless Vascular Plants

Ferns are members of the Phylum PterophytaThought to have begun

around 350 myaSurvivors of millions of

years and having 11,000 different species existing today

True vascular tissues, strong roots, and underground stems called rhizomes

Life Cycle of FernsLife Cycle of Ferns Ferns and relatives are

actually the final stage of their lifecycle Called a Diploid

Sporophyte Spores are haploid

forming young gametophytes

The gametophytes produce sperm and egg and then fertilize the egg

After fertilization, a mature sporophyte grows from the gametophyte