Plants Chapter 21

Plant Evolution Plant: multicellular, photosynthetic eukaryotic organism that contains tissues and organs with specialized structures and functions Plants share a common ancestor with green algae. Plants developed derived traits (adaptations) to be able to live on land. Cuticle Stomata Vascular tissue Reproductive strategies Seeds

PLANT LEAF performs photosynthesis Not pictured Vascular tissues: specialized transport tissues that move water and nutrients from the roots to the rest of the plant; provides support Reproductive strategies: adaptations of gametes and mutually beneficial relationships with other living things Seeds: Seed coats protect embryo of new plants as they scatter on land CUTICLE reduces water loss; STOMATA allow gas exchange (photosynthesis and cellular respiration) STEM supports plant (and may perform photosynthesis) ALGAE Surrounding water supports the algae WHOLE ALGAE performs photosynthesis; absorbs water, CO2, and minerals from the water ROOTS anchor plant; absorb water and minerals from the soil (aided by mycorrhizal fungi) HOLDFAST anchors the algae

Plant Classification Two main categories: Nonvascular Plants (earliest to diverge) Called Bryophytes Common examples: mosses, hornworts, and liverworts Small plants Lack true leaves; use root-like rhizoids to anchor them into to a surface Live in damp, shady areas to assist in providing water to tissues Vascular Plants (evolved later) Seedless Plants (ferns) and Seed Plants Contain a xylem and phloem Have well-developed root system Rigid stem

Vascular Seedless Plants - Ferns Tend to live in damp, shady areas Water is need for flagellated sperm to reach the egg to reproduce new generations of the plants.

Vascular Seed Plants The appearance of seeds is a major evolutionary step. Pollen grains transport sperm rather than water. Seed Structure – protects embryo: Seed coat: protective coating Embryo: growing, developing new plant Cotyledons: store food or help absorb food for the growing embryo Monocotyledons – have one cotyledon Dicotyledons – have two cotyledons Location of Seeds Angiosperms – seeds are found in a fruit Gymnosperms – seeds are NOT part of a fruit; naked seeds

Gymnosperms – Naked Seed Plants Gymnosperms diverged before angiosperms. Fruits are a more recent adaptation. Division Coniferophyta: Male cones produce pollen, which carries sperm. Female cones are larger and more open to allow the sperm to collect. Female cones remain on the plant until seeds are mature. When the cone drops from the tree, seeds are spread.

Angiosperms – Fruit-bearing, Flowering Plants Flowers are reproductive structures in plants. Sepal: protects flower buds Petal: attracts pollinators and provides landing pad Stamen – MALE reproductive organ; filament supports the anther; anther produces pollen (sperm) Pistil or Carpel – FEMALE reproductive organ; pollination occurs at stigma; embryo (SEEDS) develop in the ovary; fruits form from the ovary

Fruits – Seed Dispersal Fruits are seed dispersal adaptations.

Categories of Angiosperms

Categories of Angiosperms

Categories of Angiosperms Monocot is on the left Oat plant Dicot is on the right Bean plant Notice the differences in the two plants.

Categories of Angiosperms In monocots, the vascular bundles in the stem cross section are usually scattered or more complex of an arrangement as compared to dicots. The vascular bundles in the stem cross section of dicots are arranged in a circle, or ring.

Types of Monocots and Dicots