Evolution + Development

Question 1

What is a plant? (PCE)

Answer 1

• Photosynthetic
• Has cell wall
• Eukaryotic

Question 2

History of Life (GTS)

Answer 2

• 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

Question 3

The major lineages of plant evolution

Answer 3

Land plants (bryophytes, pteridophytes, gymnosperms, angiosperms)

vascular plants (pteridophytes, gymnosperms, angiosperms)

seed plants (gymnosperms, angiosperms)

Question 4

Green algae

Answer 4

• 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

Question 5

green algae example: Chlamydomonas reinhardtii

Answer 5

• 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.

Question 6

Land plants: bryophytes

Answer 6

• 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

Question 7

Life cycle of a bryophyte: moss

Answer 7

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

Question 8

Bryophyte, moss: Physcomitrella patens

Answer 8

• 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

Question 9

Pteridophytes

Answer 9

• vascular tissue (shoots, roots, and leaves)
• seedless
• life cycle: mostly sexual reproduction

Question 10

Life cycle of a seedless vascular plant: fern

Answer 10

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

Question 11

Fern: Dicksonia Antarctica

Answer 11

– > 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)

Question 12

Gymnosperms

Answer 12

• Vascular tissue (shoots, roots, and leaves)
• Naked seeds (embryo protected in seeds)
• Life cycle: mostly sexual reproduction

ex: pine

Question 13

Life cycle of a gymnosperm: pine

Answer 13

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

Question 14

Gingko biloba

Answer 14

• medicinal/ food use
• native to China
• fossils dating back 270 million years > living fossil

Question 15

Angiosperms

Answer 15

• Vascular tissue (shoots, roots, and leaves)
• Protected seeds (making flowers)
• Monocots and dicots
• Life cycle: mostly sexual reproduction

Question 16

Life cycle of a flowering seed plant

Answer 16

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

Question 17

Arabidopsis: the most popular plant, model organism

Answer 17

• 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…)

Question 18

Oryza sativa (rice)

Answer 18

• 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

Question 19

Summary of Plants Evolution

Answer 19

• 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.

Question 20

Plant growth and development

Answer 20

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.

Question 21

Plant growth and development

Answer 21

1) Embryonic:
- embryogenesis and seed dev. ( single fertilized egg to seed)
- seed germination and seedling growth (seedling)

2) Postembryonic:
- mature plant

Question 22

Postembryonic growth and development

Answer 22

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

Question 23

Stem cells and growth and development

Answer 23

Stem cells: self renewable, undifferentiated progenitor cells, have the potential to develop into tissues, organs, or a whole organism

Question 24

Plant stem cells

Answer 24

Embryonic and Postembryonic stages:

• Shoot apical meristem (SAM)
• Root apical meristem

Postembryonic stage:

• vascular cambium
• cork cambium
• root pericycle

Question 25

Regulation of plant growth and development

Answer 25

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

Question 26

Hormones

Answer 26

- 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

Question 27

Six major classes of plant hormones (ACEGBA)

Answer 27

1) Auxin 2) Cytokinins 3) Ethylene 4) Gibberellins 5) Brassinosteroids 6) Abscisic Acid

Question 28

Abiotic Factors

Answer 28

non-living physical and chemical factors that affect and organism for its growth and development

Question 29

Biotic factors

Answer 29

living organism and their derived materials that directly or indirectly affect another organism for its development and reproduction - -> viruses, bacteria, fungi, nematodes - -> insects, animals

Question 30

Differences between plants and animals in development

Answer 30

1) body plan 2) determinacy of body form 3) growth 4) regeneration 5) alternation of generations 6) mobility 7) at the cellular level

Question 31

1) body plan

Answer 31

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)

Question 32

2) determinacy of body form

Answer 32

``` 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.

Question 33

3) growth

Answer 33

- 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.

Question 34

4) regeneration

Answer 34

- 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

Question 35

4) Regeneration ---> totipotency

Answer 35

- Totipotency: tissue or cells that are capable of developing into ANY structure of the mature plant - Plant cuttings

Question 36

5) alternation of generations

Answer 36

- 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.

Question 37

6) Mobility

Answer 37

- 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.

Question 38

7) At the cellular level

Answer 38

Similarities between plants and animals 1. Cellular levels: Plants and animals share similarity in cellular organization 2. 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.