Evolution and Adaptations of Land Plants

1. KEY CONCEPTPlant life began in the water and became adapted to land.

2. Land plants evolved from green algae. • Plants and green algae have many common traits. • both are photosynthetic eukaryotes • both have the same types of chlorophyll • both use starch as a storage product • both have cell walls with cellulose

3. True plants evolved through natural selection. • Ancestral charophyceans lived in areas of shallow water. • Those that could survive longer dry periods were favored. • First true plants probably grew at edges of water. • True plants have embryos that develop while attached to female parent.

4. True plants evolved through natural selection. Analyze: 1. What category of plant evolved most recently? 2. What is the first category of plants to evolve from the ancestral charophy-ceans? 3. When did the flowering plant lineage diverge from the cone-bearing plant lineage?

5. Challenges of living on land have selected for certain plant adaptations. A cuticle allows plants to retain moisture. waxy, waterproof layer Plants have adaptations that allow them to live on land. • holds moisture in and keeps the plant from drying out

6. Stomata are small openings in the cuticle that allow for gas exchange between the plant and the atmosphere. • can open and close • allow air to move in and out

7. A vascular system allows resources to move to different parts of the plant. water and mineral nutrients sugars • collection of specialized tissues • brings water and mineral nutrients up from roots • disperses sugars from the leaves • allows plants to grow higher off the ground

8. Lignin allows plants to grow upright. lignin plant cells • hardens cell walls of some vascular tissues • provides stiffness to stems

9. Pollen grains allow for reproduction without free-standing water. • pollen grains contain a cell that divides to form sperm • pollen can be carried by wind or animals to female structures

10. A seed is a storage device for a plant embryo. • seed coats protect embryos from drying wind and sunlight • embryo develops when environment is favorable

11. Plants and other organisms can share a mutualistic relationship. a mutualism is an interaction in which two species benefit plant roots and certain fungi and bacteria flowering plants and their animal pollinators Plants evolve with other organisms in their environment. Fig. The hawk moth has a tongue that measures 30-35 cm. It is the pollinator of a night-blooming orchid whose nectar is produced 30 cm down inside the flower.

12. Plants have adaptations that prevent animals from eating them. • spines and thorns • defensive chemicals that can act as pesticides or taste bad to keep predators away

13. Nonvascular plants grow close to the ground to absorb water and nutrients. Seedless plants rely on free-standing water for reproduction. Liverworts belong to phylum Hepatophyta. often grow on wet rocks or in greenhouses can be thallose (no difference between stem or leaf) or leafy Mosses and their relatives are seedless nonvascular plants. Fig. Thallose liverworts, like the one shown here, can grow from 2 mm to 25 cm in length.

14. Hornworts belong to phylum Anthocerophyta. • found in tropical forests and along streams • flat, lobed body with little green “horns” Fig. The stalks of these hornworts are 2 to 5 cm long.

15. Mosses belong to phylum Bryophyta. • most common seedless nonvascular plants • sphagnum moss commonly used by humans as “peat” Fig. Like all nonvascular plants, mosses need to live in moist environments.

16. A vascular system allows club mosses and ferns to grow higher off the ground. Both need free-standing water for reproduction. Club mosses belong to phylum Lycophyta. Club mosses and ferns are seedless vascular plants. • not true mosses • oldest living group of vascular plants Fig. Club mosses, such as this Lycopodium species, are able to grow up off of the ground because they have vascular systems.

17. Ferns and their relatives belong to phylum Pterophyta. frond fiddlehead • whisk ferns and horsetails are close relatives of ferns • ferns have large leaves called fronds Parts of a Fern Ferns are the most common seedless vascular plants. Most have a rhizome anchored by roots, as well as leaves (fronds). Young fronds (fiddleheads) are tightly coiled. Spores are produced in sporangia on the under side of the leaves.

18. Seed plants have several advantages over their seedless ancestors. can reproduce without free-standing water, via pollination Seed plants include cone-bearing plants and flowering plants. • pollinationoccurs when pollen meets female plant parts • seeds nourish and protect plant embryo • seeds allow plants to disperse to new places Fig. Seed plants produce pollen. In pine trees such as the one shown here, clouds of pollen are released from male pine cones.

19. Gymnosperms is a seed plant that do not have seeds enclosed in fruit. • most gymnosperms are cone-bearing and evergreen. • the cone is reproductive structure of most gymnosperms. • pollen is produced in male cones. • eggs are produced in female cones. • seeds develop on scales of female cones.

20. Cycads are gymnosperms in phylum Cycadophyta. • look like palm trees with large cones • grow in tropical areas Fig. Cycads, such as the one shown here, produce seeds on large, protective, female cones.

21. Ginkgos are gymnosperms in phylum Ginkgophyta. • only one species alive today, Ginkgo biloba • grown in gardens and used in urban landscaping Fig. The name Ginkgo biloba refers to the two-lobed leaves of this plant.

22. most common gymnosperms alive today • includes pines, spruce, cedar, fir, and juniper • Conifers are gymnosperms in phylum Coniferophyta. Fig. Ponderosa pine cone. Fig. This Ponderosa pine is a typical evergreen conifer with needlelike leaves.

23. Angiosperms have seeds enclosed in some type of fruit. • A flower is the reproductive structure of angiosperms. • A fruit is a mature ovary of a flower. • Angiosperms, or flowering plants, belong in phylum Anthophyta. Fig. Many trees, including dogwoods, are flowering plants.

24. Botanists classify flowering plants into 2 groups based on seed type - Monocots OR Dicots

25. Flowering plants are also categorized by stem type and lifespan. • Herbaceous or Woody stems • 3 types of lifespans • Annual – only live for one year • Biennial – take 2 years to complete their life cycle • Perennial – any flowering plant that lives for more than 2 years Fig. Iris (left): Monocot, herbaceous, perennial, Oak (middle): Dicot, woody, perennial, Wheat (right): Monocot, herbaceous, annual

26. Botany is the study of plants. Ethnobotany explores how people in different cultures use plants. Agriculture provides stable food supplies for people in permanent settlements. Fig. Agriculture has become an important part of our global economy. Many river deltas, such as the Sacramento River delta in California, are used for farmland because of their nutrient-rich soils and water.

27. Pharmacology is the study of drugs and their effects on the body. Many drugs are derived from plants. Salicin from willow trees is used in aspirin. Alkaloids are potent plant chemicals that contain nitrogen. Alkaloids such as taxol have anti-cancer properties. Plant compounds are essential to modern medicine. Fig. This scientist, standing waist-high in water, is studying a mangrove forest in Thailand. Mangrove forests grow in intertidal zones in the tropics. These diverse ecosystems may hold treatments for a variety of medical conditions.