BIOL 1120 REEDER
The Angiosperms
I. Division Anthophyta (flowering seed plants)
A. Characteristics
1. Contains six times the number of species of all other plant groups combined: approximately 285,000
species; Earth's dominant plants
2. Size varies from the small duckweed found on pond surfaces to shrubs, vines, herbs and tree-size
3. Habitat greatly varies from deserts, mountains, polar regions, marsh and estuaries, to lakes and
streams
4. Majority are autotrophic with exceptions: Indian pipe plant that has little or no chlorophyll and is
partially or wholly parasitic to the carnivorous but photosynthetic Venus flytrap (pitcher plants,
sundews, flytraps)
5. Life cycle varies from a month to 20 to 30 years to reach sexual maturity; some live for only a single
growing season (annuals); other are perennials
6. Crucial to the existence and economy of humans: food, clothing, lumber, fuel, beverages, drugs, and
medicines (digitalis and codeine)
a. cereal crops such as rice, wheat, corn, and barley
b. valuable lumber such as oak, cherry, and walnut
c. fibers like cotton and linen
d. other products such as rubber, tobacco, coffee, chocolate and aromatic oils for perfumes
7. Most distinctive feature of its member are the flowers (sexual reproductive organ)
B. Evolution
1. Not linked clearly to any other group
2. Sprung up only once and suddenly and radiated rapidly into a variety of different forms
a. Structural and molecular data possibly indicates the gnetophytes of the gymnosperms as the
closest living relatives
3. Found abundant in the fossil record of the Cretaceous period (70 million years ago) when the earth
was drying and cooling, dinosaurs and most cycads were extinct, and mammals and angiosperms
were beginning domination
4. Great evolutionary success:
a. more efficient vascular tissue and extensive root system
b. leaves with large surface area for photosynthesis
c. seedlings can survive with less light than gymnosperms
d. speed in growth and reproduction
1) presence of closed carpels (results in fruit surrounding seeds), double fertilization, and faster
seed production increases reproductive success
e. relationships with various animals for pollination and seed dispersal due to flower attraction
1) helps to ensure cross-fertilization
f. dominant sporophyte (GAMETIC): overall adaptability to new habitats and changing
environments
C. Angiosperms Distinguished from Gymnosperms
1. Abundance and prominence of xylem vessel elements and phloem sieve tube members; most
gymnosperms have only tracheids (smaller and acutely slanted at their cell wall endings) comprising
their xylem; less efficient and specialized sieve cells comprise gymnosperm phloem.
2. Formation of flowers and fruits; most species are monoecious (male and female parts on same flower)
with some dioecious species
3. Presence of sepals, petals, or both in angiosperms
4. Formation of a pistil through which the pollen tube grows to reach the ovule and egg; in
gymnosperms, the pollen lands on the ovule surface and the pollen tube must grow in directly; ovules
develop into seeds while the ovary wall develops into the fruit in angiosperms
5. Endosperm is triploid rather than haploid as in gymnosperms; triploid is formed as a result of double
fertilization instead of prior to fertilization as in gymnosperms.
D. Angiosperm classes:
l. Dicotyledons: most vegetables, fruit and nut crops and angiospermous lumber trees (deciduous)
a. Families include buttercup (Ranunculus), mustard, rose, maple,cactus, carnation, mint, pea and
parsley.
l) Rose family includes apple, pear, plum, cherry, apricot, peach, almond and strawberry
