Hypotheses about the origin of life. which is your favorite hypothesis and why
rosio24julio
PlantsandtheconquestoflandI28129.pptxPlants & The Conquest Of Land I
Kingdom Plantae evolved within the Archeaplastida Supergroup
Common Eukaryote ancestor
Supergroup Archaeplastida Land plants and their relatives
4
Cell walls: rose-shaped complexes are used for cellulose synthesis
Plasmodesmata (channel for communications between cells) are present
Formation of a phragmoplast (forms during plant cytokinesis to allow the formation of the new cell wall separating the two daughter cells)
Sexual reproduction and structure of flagellated sperm
Peroxisome enzymes (that minimize loss of carbohydrates due to photorespiration)
4
Complex charophytes share several derived traits with land plants
4
New in true plants:
Alternation of generations
Multicellular, dependent Embryo
Walled spores produced in sporangia
Apical meristems
Although present in other green algae (chlorophytes), it was no present in charophycens, the closest relatives to plants.
It seems that alternation of generations appeared during the evolution from ancestor charophyceans to plants, beginning with a delay of meiosis
Alternation of generations
Key traits that appear in nearly all land plants but are absent in the charophytes (charophycean) include
Alternation of generations
Multicellular, dependent embryos
Walled spores produced in sporangia
Apical meristems
© 2016 Pearson Education, Inc.
Alternation of generations
Gametophyte
(n)
Mitosis
n
n
n
Spore
Gamete
Gamete from
another plant
Mitosis
n
MEIOSIS
FERTILIZATION
Zygote
2n
Sporophyte
(2n)
Mitosis
Haploid (n)
Diploid (2n)
Figure 26.6-1 Exploring alternation of generations (part 1: cycle)
© 2016 Pearson Education, Inc.
Multicellular, dependent embryos: give name embryophytes
Embryo
Maternal
tissue
Wall ingrowths
10 µm
2 µm
Placental transfer
cell (blue outline)
Embryo (LM) and placental transfer cell (TEM)
of Marchantia (a liverwort)
10 mm
2 mm
Figure 26.6-2 Exploring alternation of generations (part 2: multicellular, dependent embryos)
10
Embryo: a critical innovation
Absent from charophyceans
First distinctive trait acquired by land plants
Embryophytes a synonym for plants
3 features:
Multicellular and diploid
Zygotes and embryos retained
Depends on organic and mineral materials supplied by mother plant – placental transfer tissues
10
Spores are also present in some protists and in fungi, but plants spores are produced in a specific structure, the plant sporangia, and are covered by sporopollenin, a durable organic material that forms a wall and provides resistance to harsh conditions.
Walled spores produced in sporangia
Meristems are sites of repeated cell division of unspecialized cells. These cells differentiate, and become specialized in relation to the function they will perform.
Apical Meristems are the site of primary growth in a plant, and can be found at the root and shoot tips. Here you can find unspecialized cells, which undergo the following sequence to become a functional part of the plant
Apical meristems
Additional derived traits include:
Cuticle, a waxy covering of the epidermis that functions in preventing water loss and microbial attack
Stomata, specialized pores that allow the exchange of CO2 and O2 between the outside air and the plant
Other innovations appear later in plant evolution and are not present in all plants: Vascular tissue, seeds, pollen, flowers and fruits
© 2016 Pearson Education, Inc.
13
© 2016 Pearson Education, Inc.
Ancestral species gave rise to a vast diversity of modern plants
Figure 26.18-2 Highlights of plant evolution (part 2: art)
Bryophytes, first plants to appear
Bryophytes are anchored to the substrate by rhizoids
The flagellated sperm produced by bryophytes must swim through a film of water to reach and fertilize the egg
In bryophytes, the gametophytes are larger and longer-living than sporophytes. We say that gametophyte is the dominant generation
The height of gametophytes is constrained by lack of vascular tissues
© 2016 Pearson Education, Inc.
Capsule
Seta
Sporophyte
(a sturdy
plant that
takes months
to grow)
Gametophyte
(b) Polytrichum commune, a moss
(a) Plagiochila deltoidea, a liverwort
Sporophyte
Gametophyte
(c) Anthoceros sp., a hornwort
The dominant generation, is haploid
Figure 26.19 Bryophytes (nonvascular plants)
LE 29-8
Male
gametophyte
“Bud”
Spores develop into
threadlike protonemata.
Protonemata
“Bud”
The haploid protonemata produce “buds” that grow into gametophytes.
Raindrop
Sperm
Antheridia
Most mosses have separate male and female gametophytes, with antheridia and archegonia, respectively.
Egg
Haploid (n)
Diploid (2n)
Key
A sperm swims through a film of moisture to an archegonium and fertilizes the egg.
Archegonia
Rhizoid
Female
gametophyte
Gametophore
Spores
Sporangium
Peristome
MEIOSIS
Meiosis occurs and haploid spores develop in the sporangium of the sporophyte. When the sporangium lid pops off, the peristome “teeth” regulate gradual release of the spores.
The sporophyte grows a long stalk, or seta, that emerges from the archegonium.
FERTILIZATION
(within archegonium)
Archegonium
Zygote
Embryo
Calyptra
Young
sporophyte
Attached by its foot, the sporophyte remains nutritionally dependent on the gametophyte.
The diploid zygote develops into a sporophyte embryo within the archegonium.
Capsule
(sporangium)
Seta
Foot
Mature
sporophytes
Capsule with
peristome (SEM)
Female
gametophytes
Moss Life Cycle
17
Vascular Plants or Tracheophytes.
The presence of vascular tissue gives name to this group.
Vascular tissue: complex conducting tissue found in vascular plants. Compound by xylem and phloem
Xylem: Dead cells conducting water and minerals
Phloem: Living cells conducting nutrients derived from photosynthesis (sugar, sap: sugar-rich water solution).
Vascular plants generally possess stems, roots, and leaves having vascular tissues.
Stems: Contain vascular tissue (phloem and xylem) and lignin and produce leaves and reproductive structures
Roots: Specialized for uptake of water and minerals from the soil
Leaves: Photosynthetic function, and conservation of water.
© 2016 Pearson Education, Inc.
Microphyll leaves
Microphylls
Unbranched
vascular tissue
Selaginella kraussiana
(Krauss’s spikemoss)
Megaphyll leaves
Megaphylls
Branched
vascular
tissue
Hymenophyllum
tunbrigense
(Tunbridge filmy fern)
Figure 26.22 Microphyll and megaphyll leaves
© 2016 Pearson Education, Inc.
Liverworts
Origin of plants
ANCESTRAL
GREEN ALGA
Mosses
Hornworts
Lycophytes (club mosses,
spikemosses, quillworts)
Monilophytes (ferns,
horsetails, whisk ferns)
Gymnosperms
Origin of seed plants
Angiosperms
500
(bryophytes)
plants
Nonvascular
Vascular plants
plants
Seed
plants
vascular
Seedless
Plants
Origin of vascular plants
450
400
350
300
Millions of years ago (mya)
50
0
Ancestral species gave rise to a vast diversity of modern plants
Figure 26.18 Highlights of plant evolution
Seedless Vascular Plants
Bryophytes were the prevalent vegetation during the first 100 million years of plant evolution
The earliest vascular plants date to 425 million years ago
© 2016 Pearson Education, Inc.
The First Plants to Grow Tall
22
Seedless vascular plants can be divided into two clades
Lycophytes
(club mosses and their relatives)
Monilophytes
(ferns and their relatives)
Figure 26.20 Lycophytes and monilophytes (seedless vascular plants)
1 m
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Spore dispersal
Spore (n)
Young gametophyte
Rhizoid
Underside of mature gametophyte (n)
Antheridium
Sperm
Archegonium
Egg
FERTILIZATION
Zygote (2n)
Gametophyte
New sporophyte
Mature sporophyte (2n)
Fiddlehead (young leaf)
Sporangium
Sorus
Sporangium
The life cycle of a fern
24
Figure 29.13 The life cycle of a fern.
© 2016 Pearson Education, Inc.
PLANT GROUP
Mosses and other
nonvascular plants
Gametophyte
Reduced, dependent
on gametophyte for
nutrition
Ferns and other
seedless
vascular plants
Reduced, independent
(photosynthetic and
free-living)
Dominant
Seed plants (gymnosperms and angiosperms)
Reduced (usually microscopic), dependent on
surrounding sporophyte tissue for nutrition
Sporophyte
Dominant
Gymnosperm
Microscopic female
gametophytes (n) inside
ovulate cone
Angiosperm
Microscopic female
gametophytes
(n) inside these parts
of flowers
Microscopic
male
gametophytes
(n) inside
these parts
of flowers
Sporophyte
(2n)
Sporophyte
(2n)
Gametophyte
(n)
Example
Gametophyte
(n)
Microscopic
male
gametophytes (n)
inside pollen
cone
Sporophyte
(2n)
Sporophyte
(2n)
Dominant
pollen
Figure 26.21 Gametophyte-sporophyte relationships in different plant groups
