Biodiversity 3: land plants intro

Archaeplastida

within the supergroup is Viridiplamtae (green plants)

• have cellulose within cells walls , chl a and b and lack pigments found in red algae

Land plants description

1. chlorophylls a and b and carotenoids

2. alternation of generations

3. single egg cell with unique organ

Alternation of generation

means an organism’s life cycle switches between two stages —
one that is haploid (gametophyte) and one that is diploid (sporophyte).

So it alternates between producing gametes (sex cells) and spores.

Plants function / evolutionary history

advantage: can survive from dying out

challenge: prevent dying 

what is one method is prevent drying

waxy cuticle

1. Bryophytes

• earliest member of lands plants

• small, non-vascular

• high humidity/access to water important

include: mosses, liverworts, and hornworts

2. Vascular plants (tracheophyta)

• synapomorphy

  • vascular tissue (xylem and phloem)

• include all living ferns, tree, herbaceous plants, all flower and fruit-bearing plants

Gametophyte (1n)

produces gametes through mitosis

sporophyte (2n)

produces spores through meiosis

Why does the bryophyte sporophyte depend on the gametophyte for survival?

In bryophytes, the sporophyte grows on the gametophyte, getting water and nutrients from it. The sporangium makes spores that spread by wind.

what is the skills that early plants developed?

the ability to disperse offspring (spored) through the air

Plants vascular system

• many basic tissue types

• vascular tissues lies in a ring near the outside the stem

• extend from tip of roots through the stem and into veins within leaves

• xylem and phloem

Phloem anatomy

downward

• carries photosynthates downward from leaf to the roots

phloem sap

the sugar-rich solution

Xylem

upwards

• carry water and minerals upwards from the roots to the leaves

WHat is lignin?

secreted by these cells provides structural support

Tracheophytes (vascular plants)

ferns - seed plants

• In seed plants, the female gametophyte stays protected inside layers of tissue.

• The male gametophyte (pollen) is small and partly free-living.

Seed plants in division:

• Seed plants are divided into gymnosperms (cone-bearing) and angiosperms (flowering).

• Both belong to tracheophytes, meaning vascular plants with transport tissues.

Why are seed plants considered heterosporous, and how does this relate to the female gametophyte being retained within the sporophyte?

Seed plants make two spores (male and female); the female gametophyte stays inside the sporophyte for protection and support.

What is fertilization in plants?

Fertilization is the process where the male cell (from pollen) moves to the female cell (ovule).

Where does fertilization occur in gymnosperms?

Fertilization occurs in a seed cone for gymnosperms.

Where does fertilization occur in angiosperms?

Fertilization occurs in a flower for angiosperms.

How do seeds develop and disperse in gymnosperms?

Seeds develop on the cone and are dispersed after maturity.

How are seeds dispersed in angiosperms?

Seeds are contained in fruits (fleshy or dry) and are dispersed by animals, wind, or water.

What are pollen grains in seed plants?

Pollen grains are the immature male gametophytes of seed plants.

How are pollen grains formed?

Pollen grains are formed through meiosis, spore wall formation, and gametophyte development.

How many nuclei do pollen grains have at the time of release?

Pollen grains have 2–4 nuclei at the time of release.

What is pollination?

Pollination is the transfer of pollen from the pollen sacs to the ovule (in gymnosperms) or to the stigma of the ovary (in flowering plants).

how does pollen dispersal?

wind must transport gymnosperm pollen to a seed cone

Pollen dispersal : Angiosperms

Pollination. by wind, water, and animals of many sorts

What types of organisms act as pollen vectors for flowering plants?

Flowering plants use both insects and vertebrates as pollen vectors.

Why do pollinators visit flowers?

Pollinators visit flowers to obtain a reward, usually pollen or nectar, which is a 10–20% sugar solution.

How has co-evolution influenced flowering plants?

Co-evolution of flowers and pollinators has led to much of the diversity seen in flowering plants.

What is the main process described in this section?

The main process is pollen dispersal in angiosperms.

What general changes occur in fertilization and dispersal across land plants?

Fertilization and dispersal show trends of adaptation and change as plants evolved on land.

How do sporophytes differ among land plants?

Sporophytes vary greatly in size and appearance across different plant groups.

How are vascular plants classified?

Vascular plants are classified based on diagnostic differences in their structures.

What is the trend in the dominance of plant life cycles?

There is a shift from dominant haploid (gametophyte) stages to dominant diploid (sporophyte) stages.

How has the need for water in fertilization changed?

Over time, plants evolved a reduced dependence on free water for fertilization.

What major structural development occurred in land plants?

The development of vasculature (xylem and phloem) occurred, allowing better transport of water and nutrients.