Plant Diversity & Evolution (Outline)

• Review the Life cycle of Fungi• Characteristics of organisms in the Kingdom Plantae.• Evolution of plants: Challenges and adaptations to living on land• Highlights of plant evolution of the four groups of plants. • Distinguishing features of mosses, ferns, cone-bearing, and flowering plants.• Haploid and diploid cells and structures in plants: gametophyte and a sporophyte

genetic content, cell division and resulting cells.• Life cycle of mosses, ferns, cone-bearing, and flowering plants: Structural

adaptations• Alternation of haploid and diploid in early plants with that of later plants in relation

to:– The haploid or diploid nature of the cells making up the green leafy part of the

plant.– Cell division leading to the growth of the green leafy plant.– Presence of male and female gametes: their names reflecting mode of

dispersal for fertilization and zygote formation.• Co-dependence: evolution of animal and land plants.• Modern day importance of plants for human existence.

Classification systems

5 Kingdom system 3 Domain system1. Monera 1. Bacteria

2. Archaea2. Protista 3. Eukarya3. Fungi4. Animalia5. Plantae

Fungal groups have characteristic reproductive structures

KeyHaploid (n)Heterokaryotic (n + n)Diploid (2n)

Fusion ofnuclei

Meiosis

Basidia Spores (n)Mushroom

1 Fusion of two hyphaeof different mating types

2 Growth ofheterokaryotic mycelium

3 Diploid nuclei

4 Sporesreleased

5 Germination of sporesand growth of mycelia

• Sexual life cyclesTypes of sexual life cycles: diploid-dominant, haploid-dominant, and alternation of generations.

https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/sexual-life-cycles

Figure 15.3B

0

65

135

245

Mill

ions

of y

ears

ago

Pale

ozoi

cM

esoz

oic

Ceno

zoic

EurasiaAfrica

South America

India

Antarctica

Laurasia

Continental drift changes the land masses on earth and impact all forms of life:

altering habitats and triggered extinctions

Colonizationof land plants

Animals

Cenozoic

Origin of solarsystem andEarth

Humans

Single-celledeukaryotes Atmospheric

oxygen

Multicellulareukaryotes

Prokaryotes

Proterozoiceon

Archaeaneon

1

2 3

4

Last 0.5 bilion years

Early aquatic photosynthetic organisms

- Prokaryotic bacteria- Eukaryotic algae

Plants and green algae share a common ancestor

LM 4

44×

Highlights of plant evolution

Origin of vascular plants(about 420 mya)

Origin of seed plants(about 360 mya)

Origin of land plants(about 475 mya)

Seed plants

Land plants

Bryophytes(nonvascular plants) Vascular plants

Seedless vascular plants

Live

rwor

ts

Hor

nwor

ts

Mos

ses

Lyco

phyt

es(c

lub

mos

ses

and

rela

tives

)

Pter

ophy

tes

(fern

s an

d re

lativ

es)

Ang

iosp

erm

s

Gym

nosp

erm

s

Problems for plant life on land:

1. Water and nutrients are in the ground2. Carbon dioxide and light are above the

ground. 3. Support against the force of gravity 4. Dry conditions will dry out reproductive

cells.

Early plants thrived on moist shorelines as multicellular eukaryotic organisms developed adaptation not present in algae

Plant

Rootsanchor plant;absorb water andminerals fromthe soil

Reproductive structures, as in flowers,contain spores and gametes

Cuticle covering leaves and stemsreduces water loss; stomata inleaves allow gas exchange

Leaf performs photosynthesis

Surrounding watersupports alga

Stem supports plant and mayperform photosynthesis

Whole algaperformsphotosynthesis;absorbs water,CO2, andminerals fromthe water

Holdfastanchors alga

Alga Sea lettuce a multi cellular algae

Plants have adaptations for life on land

Access to inorganic molecules by two specialized organs

1. Roots that anchoring the plant and absorb nutrients and water from ground

2. Shoots (stems and leaves) to support the leaves that access light and CO2 for photosynthesis.

Some plants have vascular tissue to distribute water and nutrients from ground to leaves and sugar from leaves to the rest of plant body

1. Supporting the Plant Body against gravityThickened cell walls of some plant tissue- lignin

2. Protection against dehydration of plant cells-Maintaining Moisture

A waxy cuticle covers the stems and leaves of plants and helps retain water

Stomata are tiny pores in leaves that allow for gas exchange

3. Protection of gametes from dehydration Many living plants produce gametes that are encased in protective structures

Evolution of Land Plants1. Non-vascular plants - mosses2. Vascular plants

a. Seedless- fernsb. Seed forming

- naked seed- conifers (firs and pines)- Flowering plants- fruit bearing

All have a life cycle that includes a haploid and a diploid stage.

Early land plants

Bryophytes lack vascular tissue and include mosses, hornworts, and liverworts

Sporophyteplant (2n)

Key

Fertilization

Gametophyteplant (n)Haploid (n)

Diploid (2n)Sperm

Egg

Zygote (2n)

Gametes (n)

Spores (n)

Meiosis

Sporophyteplant (2n)

Key

Fertilization

Gametophyteplant (n)Haploid (n)

Diploid (2n)Sperm

Egg

Zygote (2n)

Gametes (n)

Spores (n)

Meiosis

Life cycle of a moss

KeyHaploid (n)Diploid (2n)

Spores (n) Egg (n)

Sperm (n) (releasedfrom gametangium)

Sporophytes (growingfrom gametophytes)Meiosis

Sporangium

Female

Gametophytes (n)

Fertilization

Stalk

Sporophyte (2n)

Male

Zygote (2n)

1

1

2

Mitosis anddevelopment

3

4

Mitosis anddevelopment

5

http://www.sumanasinc.com/webcontent/animations/content/moss.html

Haploid and diploid generations alternate in plant life cycles

1. The haploid gametophytes (separate male and female green leafy plants) produce gametes (eggs and sperms) by mitosis

2. The zygote develops into the diploid sporophyte (not green) on the female gametophyte plant and produces haploid spores by meiosis

3. Spores grow by mitosis into the haploid male and female gametophyte plants

MOSSES

Mosses have a dominant green gametophyte

• A mat of moss is mostly two separate haploid gametophyte plants: – female plants produce eggs– male plants produce swimming sperm

• The zygote develops on the female green gametophyte into the smaller diploid sporophyte

Ferns are seedless vascular plants with flagellated sperm (water-dependent for sexual reproduction)

FERNS

Ferns, like most plants, have a dominant sporophyte

• Sperm, produced by the male gametophyte swim to the protected egg in the female gametophyte

• Sporophyte depends on the gametophyte only very early

• Mature sporophyte is independent of gametophyte

Both the gametophyte and the mature sporophyte are green and free living

Life cycle of a fernKeyHaploid (n)Diploid (2n)

Egg (n)

Zygote (2n)

Sperm (n)(released from malegametangium)

Gametophyte (n)(underside)

Fertilization

Clusters ofsporangia

New sporophyte (2n)growing out ofgametophyte

Mature sporophyte(independent of gametophyte)

Spores (n)

Meiosis

Femalegametangium (n)

1

2

Mitosis anddevelopment

3

4

Mitosis anddevelopment

5

http://sciencelearn.org.nz/Contexts/Ferns/Sci-Media/Animations-and-Interactives/Fern-life-cyclehttps://www.youtube.com/watch?v=Fhk-Y0duNjg

Seedless plants dominated vast “coal forests”Ferns and other seedless plants once dominated ancient forests their remains formed coal

Seed plants- Have pollen grains instead of flagellated sperm - Protect their embryos in seeds

Cone-bearing

Flowering plants

• Gymnosperms Cone-bearing -naked seed plants • Conifers• Gingkos• Cycads

A pine tree is a sporophyte (diploid) with tiny gametophytes (haploid) in its cones

A male gamete is a pollen grain (does not swim) fertilizes an ovule in the female gametophyte

The zygote develops into a sporophyte embryo and becomes a seed, with stored food and a protective coat

http://life9e.sinauer.com/life9e/pages/29/292001.html

Cone-bearing plants

Life cycle of a pine tree

KeyHaploid (n)Diploid (2n)

Zygote(2n)

Fertilization

Mature sporophyte

Pollen grains (malegametophytes) (n)

Meiosis

Female gametophyte (n)

Eggs (n)Sperm (n)Male gametophyte(pollen grain)

Seed coat

Embryo(2n)Foodsupply

Seed

Ovule

Scale

Meiosis

Sporangium (2n)Spore mother cell (2n)

Integument

Female conebears ovules.

1

Sporangia in male coneproduce spores by meiosis;spores develop into pollengrains.

2

Pollination3

A haploid spore cell inovule develops intofemale gametophyte,which makes eggs.

4

Male gametophyte(pollen) grows tubeto egg and makesand releases sperm.

5

Zygote developsinto embryo, andovule becomes seed.

6

Seed germinates,and embryo growsinto seedling.

7

http://life9e.sinauer.com/life9e/pages/29/292001.html

Dispersal of pollen and fertilized naked seeds depends on wind

Both pollen and seeds of gymnosperms have wing-like structures and can be airborne

• Angiosperms • The angiosperm plant is a sporophyte with

gametophytes in its flowers

• The flower is the centerpiece of reproduction

• A male gamete is a pollen grain (does not swim) fertilizes an ovule in the female gametophyte

• The flower is modified into a fruit once fertilization takes place, with the zygote developing into a sporophyteembryo and becomes a seed, with stored food and a protective coat

Flowering plants

Flowers usually consist of: sepals, petals, stamens (which produce pollen), and carpels(which produce eggs)

Anther

FilamentStamen

Petal

Receptacle Ovule

Sepal

Stigma

StyleOvary

Carpel

Life cycle of an angiosperm

Sperm

Pollen grains (n)Meiosis

Meiosis

Stigma

Pollen grainPollen tube

Egg (n)

Ovule

Fertilization

Embryo(2n)

Foodsupply

Seedcoat

Seeds

KeyHaploid (n)Diploid (2n)

Sporophyte (2n)Ovule Ovary

StigmaAnther

1Haploid spores in anthers develop into pollen grains: male gametophytes.

2 Haploid spore in each ovuledevelops into female gametophyte,which produces egg.

3 Pollination andgrowth ofpollen tube

4 Zygote(2n)

5 Seed

6 Fruit(mature ovary)

7 Seed germinates,and embryogrows intoplant.

http://life9e.sinauer.com/life9e/pages/29/292002.html

Angiosperms evolved in the presence of insects and other animals

1. Pollen has no wing-like structures.Depend on insects and birds for pollination.

2. Seeds don’t have wing-like structure. Depend in addition on dispersal by animals either physically or by eating fruits and dispersing their seeds over long distance with their feces.

3. Interactions with animals have profoundly influenced flowering plant evolution, a major source of food for animals

Animals also aid plants in pollination

The structure of a fruit reflects its function in seed dispersal fruits are adaptations for seed dispersal

Angiosperms provide

1. food produced by agriculture 2. important medicinal products

Some plants in these forests contain chemicals that have medicinal uses