plant evolution, extinction and hybridization

EVOLUTION OF EARLY LAND

PLANTS

Reported by: Crisanta Montejo

At the end of the lesson students are expected to:

a. trace the evolution modification of plants throughout timeb. Determine the different plant group per evolutionary modification and characteristicsc. understand the process of hybridization among plantsd. explore what causes plants to extinctione. value the diversity of life which is the product of evolution throughout time

BIODIVERSITY AND EVOLUTION

The great diversity of life is the PRODUCT of evolution.

It represents the aquatic plants thus pushing the curiosity of mankind to try to explain the origin of plants and bow it colonized the world since the beginning.

PIONEERS IN A NEW WORLD

Cyanobacteria were probably first to produce oxygen Later, green algae evolved and gave rise to plants

Ancestors of Plants

*Charophytes Evidences like both plants and green algae have chlorophyll b, same type of chloroplasts, cell wall structure, sequence in DNA and cell plate during cell division

EVIDENCES THAT SUPPORT PHYLOGENETIC CONNECTION OF LAND PLANTS AND GREEN ALGAE

Homologous chloroplasts presence of chlorophyll b and beta-carotene and thylakoids stackes as grana.

Homologous cellulose walls Celloluse comprises 20-26% of the cell wall

Homologous peroxisomes both land plants and charophycean algae package enzymes that minimize the costs of

photorespiration in peroxisomes

Phagmoplasts these plate-like structures occur during cell division only in land plants and charopyceans

Molecular systematics In addition to similarities derived from a comparisons of chloroplasts genes, analyses of

several nuclear genes also provide evidence of a Charophycean ancestry of plants

ADVANTAGES AND DISADVANTAGES OF LIFE ON LAND

Sunlight unfiltered by water and plankton

Atmosphere had more CO2 than water

Soil was rich in mineral nutrients

Originally relatively few herbivores and pathogens

Relative scarcity of water Lack of structural support

against gravity

Advantages: Disadvantages:

Adaptations of plants to survive in the land:

Cuticle – substance made from cutin, waxy covering that prevents water lossStomata – part of the plants’ leaves use for gas exchange Vascular tissue – tube that transport materials throughout the plant, xylem

and phloem Lignin – chemical that hardens the plant cell wall for the plant to grow upright Seeds – provide an embryo plant with food and protection Flowers and Fruits – aid in the reproduction of plants and protect the seeds Alternation of Generation – plants develop life cycle Apical Meristem – evolution of rhizoids to true roots


Waxy cuticle – evolved to assist plant to conserve water on dry, hot days.

Stomata – evolved to allow control of water loss and transport of gases.

Vascular tissues - evolution of roots and shoots forming components – xylem and phloem for transporting water and sugars to all tissues.


o Lignin – chemical that hardens the plant cell wall for the plant to grow upright

o Apical Meristem – evolution of rhizoids to true roots

Adaptations of plants to survive in the land:Evolutionary Trends in reproduction:

Algae reproduce in water so gametes are carries by water, form zygotes in water and disperse in water. Ie No protection from dehydration required

Land plants needed: Transport gametes (pollen, flowers) Protection from drying out (seeds) Dispersal (seed coats & fruits)

Adaptations of plants to survive in the land:EVOLUTIONARY TRENDS IN PLANT LIFE CYCLES:

Alternation of Generations = haploid gametophytes produces sex cells by mitosis. Gametes unite to from a diploid zygote, which develops into diploid sporophyte that develops haploid spores by meiosis

An Overview of Land Plant Evolution

Main groups of Plants1.Non-vascular Plants (Bryophytes)2.Seedless Vascular Plants

Gymnosperm (plants-cones) Angiosperm (Flowering plants


Non-Vascular Plants (Bryophytes)

Has 3 classifications namely; MOSSES, LIVERWORTS and HORNWORTS

Has cuticle, often to water and ground for nutrients and reproduction by means of spores, have rhizoids for anchoring.

In bryophytes, the gametophyte are nutritionally independent of the sporophytes

Emerge in the mid Paleozoic era.

Mosses


Seedless Vascular Plants Has 3 classifications namely; FERNS,

HORSETAIL and CLUB MOSSES Has cuticle, vascular tissue, lignin for

plants’ foundation and usually reproduce with the use of spores

The gametophyte generation underwent a progressive reduction in size –the sporophyte phase became dominant

Emerge in late Paleozoic era (late Devonian-early Permian), Carboniferous period

Examples of Seedless Vascular PlantsHorsetail(Sphenophyta)

Ferns (Pterophyta)


Gymnosperm Conifers, cycads, ginkgoes, gnetophytes Large, cone-bearing seed plants that exist as

tees in forests Dominant sporophyte bears pollen cones,

seed cones and bear ovules which develop into “naked” seeds

Gymnosperm Diversity• Cycads

Gymnosperm Diversity• Ginkgos


Angiosperm(flowering plants) Diverse seed plants of all sizes living in all

habitats Dominant sporophyte bear flowers, with

pollen grains and bear ovules with an ovary; produced “covered” seeds

Evolved at the beginning of Cenozoic Era

HYBRIDIZATION OF PLANTS

Hybridization is the process of interbreeding between individuals of different species (interspecific hybridization) or genetically divergent

individuals from the same species (intraspecific hybridization).

was the basis of Gregor Mendel’s historic experiments with garden peas.

- Josef Kölrueter, the first to study plant hybridization

who published the results of his experiments on tobacco in 1760.

Hybrid generally refers to any offspring resulting from the breeding of two genetically distinct individuals.

monohybrid cross - is a cross when only one trait and its two alternative forms are considered during hybridization experiment 1.Purple flowered male plant is crossed with white flowered female plant 2 . Tall male plant is crossed with dwarf female plant

• SELECTION OF PURE BREEDING PARENTS• Emasculation • Bagging• Seed setting • Collection of seeds • Raising of F1 generation plants• F1 plants self pollinated • Seed setting of F1 plants• Collection of seeds from F1 plants • Raising F2 generation plants • Raising F3Plants →F4 plants→F5 plants →→F7 plants.

Plant Hybrids

In the Philippines hibiscus or gumamelas are very common. Inidividual hybrids are not named, and no one knows how many different hybrids there are. This is a sampling of some of the many, many Philippine gumamelas.

Hibiscus rosa-sininsis

EXTINCTION OF RARE PLANTSRoyal Poinciana

Extinction

is the end of a group of organisms (taxon), normally a species is generally considered to be the death of the last individual of the group (although the capacity to breed and recover may have been lost before this point).

CAUSES OF EXTINCTION

Genetics and demographic phenomena

Genetic pollution

Habitat degradation

Predation, competition, and disease

Coextinction

Global warming

List of Extinct Plants

Sigillaria–extinct: ~300 mya Araucarioxylon arizonicum–extinct: ~200 mya

List of Extinct Plants

Saint Helena Olive–extinct: 1994 in the wild

Wood’s Cycad–extinct: 1916 in the wild

THANK YOU!

plant evolution, extinction and hybridization

Education