Plant Diversity I Chapter 29

Slide 2 of 18 Evolution  Land plants descended from Chlorophyta  Green Algae  Specifically Charophyta  Plant-like Protists  Generalized Phylogenetic Relationship: Charophyta  Bryophyta  Seedless Vascular Plants  Gymnosperms  Angiospems

Slide 3 of 18 How do we know?  Charophytes  land plants  Cellulose production is identical, but unique to these 2 groups  Unique peroxisome structure & enzyme production  Sperm structure is closely related  Similar cell plate production  Nuclear and chloroplast genes are closely related

Slide 4 of 18 Movement to land…  Advantages  Increased Sunlight  In water it is attenuated and/or refracted  Increased availability of CO 2  Nutrient rich soil medium  Disadvantages  Risk of desiccation  Less water available  Gravitational force has greater effect

Slide 5 of 18 Plants are…  Suppliers of oxygen to all other terrestrial organisms  Terrestrial producers  Serve as food source for animals & fungi  Alternation of generations  Diploid and haploid life stages  Diploid = sporophyte  Haploid = gametophyte

Slide 6 of 18 Alternation of generations  Sporophyte (2n or Haploid)  Produces spores (n) by Meiosis  Spores grow into Gametophyte (n)  Mitosis  Gametophyte (n) produces gametes (n)  Gametes (n) fuse in fertilization  Zygote (2n) is produced  Mitosis = Sporophyte (2n)

Slide 7 of 18 Gametangia  Gamete production occurs in specialized organs called gametangia  Male gametangia = antheridia (antheridium)  Only male deer (bucks) have antlers  Female gametangia = archegonia (archegonium)  Land plants called embryophytes since zygote develops inside female

Slide 8 of 18 Land Plants (4 groupings)  Bryophyta – non-vascular plants so they are very small in size & live in moist environments  Seedless vascular plants – ferns  Still reside in moist, cooler environments  Waxy covering protects from desiccation  Gymnosperms (naked seeds) – Confers bear cones  Angiosperms (Covered seeds) – fruits & flowers

Slide 9 of 18 Bryophyta  First land plants – evolved from Chlorophytes  Mosses, liverworts, hornworts (no Hogwarts)  Concerned with water loss since not living in water anymore  2 Adaptations to deal with water retention  Waxy cuticle cover  Gametes packaged in structures called gametangia

Slide 10 of 18 Moar Bryophyta!!  Nonvascular plant  The lack of vascularity & flagellated sperm = dependence on water  Bryophytes live in damp areas  Spend the majority of their life in the gametophyte (haploid) stage  Rhizoids anchor the gametophyte  Long single tubular cells  Does not absorb water or nutrients like roots do

Slide 11 of 18

Slide 12 of 18  Only plants with gametophyte as dominant part of life cycle  Sporophytes basically live off the gametophyte, but do photosynthesis

Slide 13 of 18 Questions  What is the phylogenetic progression in plants?  Chlorophyta is in which Kingdom?  What is the male gametangia called?  What is the female gametangia called?

Slide 14 of 18 Seedless Vascular Plants  Xylem & Phloem – Plant vascularity  Xylem transports water throughout the plant and takes minerals from the soil to the photosynthetic areas of plants  Phloem transports sugar and nutrients to the various plant structures  Vascularity developed as plants needed to be tall for photosynthesis, but also needed to uptake water & nutrients from the soil  Common example = ferns

Slide 15 of 18 Seedless Vascular Plants (Page 2)  Vascularity allowed for taller plants  Outcompete other plant types for sunlight  Still need to be in damp environment for sperm to reach egg  Dominant stage is sporophyte  Pterophyta – may be source of carbon that is now coal  Proliferated during the Carboniferous period of late Paleozoic era

Slide 16 of 18 Homo vs. Hetero  Major Seedless plants are ferns  Ferns are homosporous  Homosporous means single spore production that gives rise to bisexual gametophytes  Homosporous  heterosporous  Heterosporous – 2 spore types  Some produce male gametophyte (microspores)  Some produce female gametophytes (macrospores)

Slide 17 of 18 Sporangia -- Site of mieosis Sporophyte (2n)  spores (n)

Slide 18 of 18 Questions 1. As we go from bryophytes to seedless vascular plants, the dominant generation of the life cycle goes from __________ to __________ 2. What is the advantage of branched sporophytes? 3. We will see: homosporous (seedless vascular plants)  ____________