Adapting to Terrestrial Living

2. Adapting to Terrestrial Living ~ 288,700 species of plants are now in existence These are terrestrial However, green algae, the likely ancestors of plants, are aquatic and not well adapted to living on land Three challenges had to be overcome 1. Mineral absorption 2. Water conservation 3. Reproduction on land

3. Plants require relatively large amounts of six inorganic minerals Nitrogen, potassium, calcium, phosphorus, magnesium, sulfur Plants absorb these materials through their roots The first plants developed symbiotic associations with fungi These mycorrhizae enabled plants to extract minerals from rocky soil Mineral Absorption

4. To avoid drying out, plants have a watertight outer covering, termed the cuticle Water Conservation

5. Spores developed as a means to protect gametes from drying out on land In a plant life cycle, there is alternation of generations Diploid with haploid Reproduction on Land

6. The diploid generation is called the sporophyte The haploid generation is called the gametophyte As plants evolved, the sporophyte tissue dominated

7. Plant Evolution Four key evolutionary innovations serve to trace the evolution of the plant kingdom

8. Plant Evolution

10. Nonvascular Plants Only two phyla of living plants lack a vascular system

12. The Evolution of Vascular Tissue The first vascular plant appeared approximately 430 million years ago (mya)

13. Early vascular plants exhibited primary growth Growth by cell division at the tips of the stem and roots About 380 mya, vascular plants developed a new pattern of growth, secondary growth New cells are produced in regions around the plant�s periphery Thus, plants could become thick-trunked and taller Note The product of plant secondary growth is wood

14. Seedless Vascular Plants Two phyla of modern-day vascular plants lack seeds Ferns (Phylum Pterophyta) Club mosses (Phylum Lycophyta) Both have free-swimming sperm that require free water for fertilization By far, the largest group are ferns ~ 12,000 living species

15. Ferns have both gametophyte and sporophyte individuals, each independent and self-sufficient Gametophyte Produces eggs and sperm These unite to form the zygote, which develops into the sporophyte Sporophyte Bears and releases haploid spores These germinate to form gametophytes The Life of a Fern

17. Evolution of Seed Plants Seeds are embryo covers that protect the embryonic plant at its most vulnerable stage Seed plants produce two kinds of gametophytes

18. All seed plants are derived from a single common ancestor There are five living phyla

19. A seed has three parts 1. A sporophyte plant embryo 2. A source of food for the embryo called endosperm 3. A drought-resistant protective cover

20. Seeds have greatly improved the adaptations of plants to living on land 1. Dispersal Facilitate migration dispersal 2. Dormancy Postpone development until conditions are favorable 3. Germination Permit embryonic development to be synchronized with habitat 4. Nourishment Offer an energy source of young plants

21. Gymnosperms Gymnosperms are nonflowering seed plants They include four phyla Conifers (Coniferophyta) Cycads (Cycadophyta) Gnetophytes (Gnetophyta) Ginkgo (Ginkgophyta)

25. Conifer trees form two kinds of cones The Life of a Gymnosperm

27. Rise of the Angiosperms Angiosperms comprise 90% of all living plants > 300,000 species Virtually all our food is derived, directly or indirectly from them In gymnosperm reproduction, pollen grains are carried passively by the wind Angiosperms have evolved a more direct way of transferring pollen Induce animals to carry it for them How? Flowers!

28. Rise of the Angiosperms Flowers are the reproductive organs of angiosperms A flower employs bright colors to attract insects and nectar, to induce the insects to enter the flower There they are coated with pollen grains, which they carry with them to other flowers

29. A flower consists of four concentric circles, or whorls, connected to a base called the recepatcle Outermost whorl (Sepals) Protects flower from physical damage Second whorl (Petals) Attracts pollinators Third whorl (Stamens) Produces pollen grains in the anther Innermost whorl (Carpel) Produces eggs in the ovary Rising from the ovary, is a slender stalk, the style, with a sticky tip, the stigma

31. Why Are ThereDifferent Kinds of Flowers? Different insect pollinators are attracted to specific types of flowers The most numerous insect pollinators are bees Bees are first attracted by the odor of nectar They then focus on the flower�s color and shape Bee-pollinated flowers are usually yellow or blue

33. Other pollinators include Moths Attracted to scented, white or pale-colored flowers

34. Improving Seeds:Double Fertilization Within their seeds, angiosperms produce a special, highly nutritious tissue called the endosperm The male gametophyte contains two sperm

36. Angiosperms are divided into two groups

37. Angiosperms are divided into two groups

38. Improving Seed Dispersal:Fruits