Today: - Lab Review - More on the Pterophytes, Gymnosperms, and Angiosperms!

Lab Review: Image 1: What is this? Haploid or diploid? What comes next in the lifecycle? Image 2: What is this? Haploid or diploid? What comes next in the lifecycle?

Lab Review: Image 3: What is this? Haploid or diploid? What comes next in the lifecycle?

Lab Review: Image 4: What is this? Haploid or diploid? What comes next in the lifecycle?

Onto The Vascular Plants: Specifics

Phylum Lycophyta The lycophytes (also called club mosses or ground pines) originally consisted of 2 groups: Small herbaceous plants and Giant woody trees Giant Lycophytes are extinct!

An artist’s vision of a forest of giant lycophytes (during a storm). These giant “trees” (30+ meters) were a dominant component of the forests of the late Carboniferous (~300 mya) from Life Before Man by Zdenek V. Spinar, illustrated by Zdenek BurianLife Before Man

Phylum Pterophyta (Ferns and Their Relatives): Three Major Groups: 1. The Psilophytes (whisk ferns) lack true leaves and roots (evolved secondarily?) may be terrestrial or epiphytic

Three Major Groups: 2. The Sphenophytes (horsetails) Also larger and more diverse during the Carboniferous period Common in waterlogged soils (have internal air canals) Phylum Pterophyta (Ferns and Their Relatives):

Horsetails: Abundant in the fossil record (also up to 30 m). Represented today by a single genus, Equisetum.

A Typical Horsetail Lifecycle

Three Major Groups: 3. The “True” Ferns: most widespread and diverse of the pteridophytes large, extensively branched vascular systems Phylum Pterophyta (Ferns and Their Relatives):

Evolution of Land Plants: A Review

The Gymnosperms “Naked Seeds” 3 Major Adaptations: 1. Continued reduction of gametophyte 2. Evolution of the seed 3. Evolution of pollen Arabidopsis thaliana pollen grains Microscopy by Juergen Berger, computer image manipulation by Heiko SchoofJuergen Berger

1. Reduction of the Gametophyte

Why keep the gametophyte?? Is the haploid gametophyte a good genetic screen?? Is the sporophyte too dependent on the gametophyte??

2. Evolution of the Seed SEED = sporophyte embryo packaged with a food supply in a protective coat. The fossilized remains of the Jeholornis prima, shown in an illustration, included about 50 well-preserved seeds in the bird's stomach. (CNN.com) Why are seeds such a great advantage??

2. Evolution of the Seed All seed plants are heterosporous Megaspores (+ female gametophytes) retained within parent sporophyte!

OVULE OVULE (Integument + Megaporangium + Megaspore) After fertilization, the ovule develops into a SEED. 2. Evolution of the Seed

3. Evolution of Polle n Microspores develop into pollen grains Pollen grains mature to become male gametophtyes Transfer of pollen to ovule = pollination Doesn’t require water!!

Gymnosperms Ovules and seeds develop of the surface of specialized leaves called sporophylls

Gymnosperm Evolution

Gymnosperm Diversity Four extant phyla: 1. Ginkophyta 2. Cycanophyta 3. Gnetophyta 4. Coniferophyta One remaining species! Popular ornamental (pollution resistant) Produces Gingko and stinky, fleshy seeds

Gymnosperm Diversity Few species of tropical, palm-like trees Symbiotic with N-fixing bacteria Toxic to livestock! Four extant phyla: 1. Ginkophyta 2. Cycanophyta 3. Gnetophyta 4. Coniferophyta

Gymnosperm Diversity 3 very different genera: Welwitschia, Gnetum, and Ephedra Four extant phyla: 1. Ginkophyta 2. Cycanophyta 3. Gnetophyta 4. Coniferophyta

Government announces ban on ephedra Wednesday, December 31, 2003 Posted: 7:58 AM EST (1258 GMT) The debate over the safety of ephedra heated up after pitcher Steve Bechler died February 17.

Gymnosperm Diversity Largest group (pines firs, spruces, larches, yews, junipers, cedars, cypresses and redwoods) Mostly evergreen; dominant in N. hemisphere where growing seasons are relatively short Four extant phyla: 1. Ginkophyta 2. Cycanophyta 3. Gnetophyta 4. Coniferophyta

A Gymnosperm (Coniferophyta) Life Cycle

Thought Question For You… Why to Conifers do so well here? Shouldn’t they be outcompeted by the angiosperms (flowering trees)??

Cool Coniferous Adaptations

Into the Angiosperms!

Minor Modifications Both gymnosperms and angiosperms use tracheids in their xylem Angiosperms also use vessel elements, and reinforce with fiber cells !

Major Modification: the Flower 4 circles of modified leaves: 1.Sepals 2.Petals 3.Stamens 4.Carpels

Fruits are Mature Ovaries Fruits protect seeds and aid in their dispersal Ovary wall becomes the pericarp (thickened wall of the fruit)

Fruits are Mature Ovaries

Hypothetical Origin of the Carpel

Types of Fruit 1. Simple Fruit- derived from a single ovary 2. Aggregate Fruit- derived from a single flower with several carpels 3. Multiple Fruit- develops from a group of flowers tightly clustered together (inflorescence)

The Angiosperms Evolution of the Flower! Traditional taxonomy = 2 Classes MonocotsandDicots Jack-in-the-Pulpit, Arisaema triphyllum

Not Monophyletic!

Angiosperm Lifecycles Like the Gymnosperms: Heterosporous Heterosporous Flower of the sporophyte produces microspores (will form male gametophytes) and megaspores (will form female gametophytes) Flower of the sporophyte produces microspores (will form male gametophytes) and megaspores (will form female gametophytes)

Angiosperm Lifecycles In Angiosperms, Each pollen grain has two haploid cells Ovules develop within the ovary, contain the female gametophyte or embryo sac (Even further reduction of gametophyte generation!)

Double

Useful Animation?? At left, Germinating Pollen Grain from a Lily, Sauromatum guttatum (SEM x3,300). This image is copyright Dennis Kunkel at used with permission.

Cross-Pollination Some flowers can self- pollinate, but most use diverse strategies to ensure cross-pollination

Angiosperms Shape Evolution By the end of the Cretaceous (65 mya) angiosperms are the dominant plants on Earth. Plants and their pollinators and dispersers are a good example of coevolution (mutual evolutionary influence)

Other Notes about Angiosperms - Ecologically important - Major human food source - Major human food source - Source of unique secondary compounds (drugs!) - Source of unique secondary compounds (drugs!) Diversity is a non-renewable resource!