Evolution + Development Flashcards
What is a plant? (PCE)
- Photosynthetic
- Has cell wall
- Eukaryotic
History of Life (GTS)
- boundaries between units in the Geologic Time Scale are marked by dramatic biotic change
- plants are eukaryotes
Time:
Humans appeared on earth around 11:58:43 pm
Land plants appeared on earth around 9:52 pm
The major lineages of plant evolution
Land plants (bryophytes, pteridophytes, gymnosperms, angiosperms)
vascular plants (pteridophytes, gymnosperms, angiosperms)
seed plants (gymnosperms, angiosperms)
Green algae
- closely related to land plants and are believed to be the origin of land plants
- most primitive plants, share characteristics with higher plants and microbes
- diverse habitats: aquatic and non-aquatic
- forms: unicellular, few-celled, filaments, flat sheet parenchytamous
- reproduction: both sexual and asexual
green algae example: Chlamydomonas reinhardtii
- Unicellular (single-celled), green algal model species
- found in diverse conditions
- they are haploid - dominant life form > diploid.
- Used to study photosynthesis, motility,
responses to stimuli such as light, and cell-cell
recognition > apply to more complex plants and
animals.
Land plants: bryophytes
- Simple land plants
- no true roots/leaves, lack vascular system, no structural support
- Have simple structures, such as water conducting cells, cuticles, stomata
- Life cycle: mostly sexual reproduction
moss: Physcomitrella patens
- -> goes through both haploid (gametophyte - 1n) and diploid (sporophyte - 2n) stages
Life cycle of a bryophyte: moss
Gametophytes (haploid, gamete producing) (1n) Sporophytes (diploid, spore producing) (2n)
Sporophytes: diploid, spore producing, smaller, short-lived, some nutritionally dependent on gametophytes
Gametophytes: haploid, gamete producing, larger, long-lived, and photosynthetic
Bryophyte, moss: Physcomitrella patens
- Multicellular organisms alternating between dominant haploid gametophyte and small/short-lived diploid sporophyte
- Important for studies on plant evolution, development, and physiology
- –> No vascular tissue, true roots/stems/leaves, and flowers and seeds.
- –> Has many intact signaling pathways found in angiosperms
- Highly efficient homologous recombination > allow genes for replacement and elimination
Pteridophytes
- vascular tissue (shoots, roots, and leaves)
- seedless
- life cycle: mostly sexual reproduction
Life cycle of a seedless vascular plant: fern
mostly sexual reproduction:
plants reproduce using haploid, unicellular spores instead of seeds
- The life cycle of seedless vascular plants is an alternation of generations, where the diploid sporophyte alternates with the haploid gametophyte phase.
Gametophytes (haploid, gamete producing) (1n) Sporophytes (diploid, spore producing) (2n)
Sporophytes: diploid, spore producing, smaller, short-lived, some nutritionally dependent on gametophytes
Gametophytes: haploid, gamete producing, larger, long-lived, and photosynthetic
Fern: Dicksonia Antarctica
– > An evergreen tree fern native to eastern Australia
• Typically grow to about 4.5–5 m (15–16 ft),
• Reproduction primarily from spores,
• Can grow in a variety of conditions (acid, neutral and alkaline, semi-shaded, dry etc)
Gymnosperms
- Vascular tissue (shoots, roots, and leaves)
- Naked seeds (embryo protected in seeds)
- Life cycle: mostly sexual reproduction
ex: pine
Life cycle of a gymnosperm: pine
Gametophytes (haploid, gamete producing) (1n) Sporophytes (diploid, spore producing) (2n)
Sporophytes: diploid, spore producing, smaller, short-lived, some nutritionally dependent on gametophytes
Gametophytes: haploid, gamete producing, larger, long-lived, and photosynthetic
Gingko biloba
- medicinal/ food use
- native to China
- fossils dating back 270 million years > living fossil
Angiosperms
- Vascular tissue (shoots, roots, and leaves)
- Protected seeds (making flowers)
- Monocots and dicots
- Life cycle: mostly sexual reproduction
Life cycle of a flowering seed plant
Gametophytes (haploid, gamete producing) (1n) Sporophytes (diploid, spore producing) (2n)
Sporophytes: diploid, spore producing, smaller, short-lived, some nutritionally dependent on gametophytes
Gametophytes: haploid, gamete producing, larger, long-lived, and photosynthetic
Arabidopsis: the most popular plant, model organism
• Has a small genome (ca. 108 bp) and about 25,000 genes • Has a short life cycle • Very small in size • Easy to grow and manipulate • Wonderful resources (mutants, genes, microarray, and proteomics…)
Oryza sativa (rice)
- Staple food for Asian countries
• Domestication is around 8,200 to 13,500 years ago.
• Two major subspecies: japonica and indica variety
• Rice occurs in a variety of colors,
• Easy for genetically modification, used as
a model organism for cereal biology
Summary of Plants Evolution
• Plants are eukaryotic organisms that perform photosynthesis. Plant cells have cell wall.
• Plants have diverse forms:
Unicellular – multicellular
Aquatic – land
Nonvascular - vascular
Haploid, diploid, polyploid
No seeds, naked seeds, protected seeds
• Reproduction of plants can be asexual and/or sexual, dominant gametophytes to dominant sporophytes.
Plant growth and development
life cycle of a flowering seed plant
The major stages of the flower life cycle are the seed, germination, growth, reproduction, pollination, and seed spreading stages. The plant life cycle starts with a seed; every seed holds a miniature plant called the embryo. There are two types of flowering plant seeds: dicots and monocots.
Plant growth and development
1) Embryonic:
- embryogenesis and seed dev. ( single fertilized egg to seed)
- seed germination and seedling growth (seedling)
2) Postembryonic:
- mature plant
Postembryonic growth and development
Organ: Tissues are grouped into organs.
Tissue: individual cells form distinct functional structure
Cell types: individual cells with distinct function.
root system and shoot system
Stem cells and growth and development
Stem cells: self renewable, undifferentiated progenitor cells, have the potential to develop into tissues, organs, or a whole organism
Plant stem cells
Embryonic and Postembryonic stages:
- Shoot apical meristem (SAM)
- Root apical meristem
Postembryonic stage:
- vascular cambium
- cork cambium
- root pericycle
Regulation of plant growth and development
central dogma: DNA –> RNA –> protein
Gene: a functional unit of DNA, consists of a fragment of DNA. The function of a gene can be executed at the RNA or protein level.
- -> Normal development requires the coordination of thousands of genes
- -> Mutations in individual genes can lead to abnormal development
Hormones
- naturally occurring small molecules
- active at low concentrations (micro M)
- production and action may be in different cells
- multiple effects, complex interactions
- six major classes
Six major classes of plant hormones (ACEGBA)
1) Auxin
2) Cytokinins
3) Ethylene
4) Gibberellins
5) Brassinosteroids
6) Abscisic Acid
Abiotic Factors
non-living physical and chemical factors that affect and organism for its growth and development
Biotic factors
living organism and their derived materials that directly or indirectly affect another organism for its development and reproduction
- -> viruses, bacteria, fungi, nematodes
- -> insects, animals
Differences between plants and animals in development
1) body plan
2) determinacy of body form
3) growth
4) regeneration
5) alternation of generations
6) mobility
7) at the cellular level
1) body plan
body plan is the the ultimate size, shape, and structure of an
organism; set up by the establishment of one or more axes
–> in animals, the major body axes: anterior/posterior (top/bottom), dorsal/ ventral (back/front), left/right
–> in plants, the main axes are: apical/basal (top/bottom), adaxial/abaxial (tip/ node), radial (left/right)
2) determinacy of body form
animal body form is completely determinant, established during embryogenesis (except larval-adult transitions).
plants: more fluid, or “plastic”, largely determined after
embryogenesis, affected by environmental factors.
3) growth
- Animals grow by proportional growth. Many animal cells
can divide and most can be replaced via cell division of
adjacent cells when they are damaged or die. - Plants grow is controlled by a few cells (meristems or
stem cells). Differentiated plant cells cannot be
replaced simply by cell division of adjacent cells.
4) regeneration
- Animal cells have limited
regeneration capacity. - Most plant cells have a much greater capacity to dedifferentiate (become LESS specialized) and redifferentiate (produce multiple specialized cell types) than do animal cells.
–> Totipotency
4) Regeneration —> totipotency
- Totipotency: tissue or cells that are capable of
developing into ANY structure of the mature plant - Plant cuttings
5) alternation of generations
- Most animals are diploid except some insects.
Haploid cells are found only in sex cells.
• Plants can switch between stages of
haploidism, diploidism, and polyploidism during
their life cycles.
6) Mobility
- Animals can move.
• Some animal cells can migrate.
• Land plants are sessile (immobile/fixed in one place).
• Plant cells cannot move once they are formed.
7) At the cellular level
Similarities between plants and animals
- Cellular levels: Plants and animals share similarity in
cellular organization - Molecular levels: Plants and animals share similar
chromosomal structure and DNA, RNA, and protein
sequences.
–> Plants have eukaryotic cells with large central vacuoles, cell walls containing cellulose, and plastids such as chloroplasts and chromoplasts.
–> Structurally, plant and animal cells are very similar because they are both eukaryotic cells. … Beyond size, the main structural differences between plant and animal cells lie in a few additional structures found in plant cells. These structures include: chloroplasts, the cell wall, and vacuoles.
