Week 4

Question 1

timeline of principal adaptive traits that evolved in the tree of life over the first 90% of the history of life on earth

Answer 1

• archaea + bacteria
  
  • oldest fossils
• photosynthesizers
  
  • purple/green sulfur bacteria
• cyanobacteria
  
  • which produce oxygen gas during photosynthesis
• nucleus formation and primary endosymbiosis with ancestral mitochondria
  
  • caused aerobically respirating bacteria
• primary endosymbiosis with ancestral cyanobacteria
  
  • photosynthetic eukaryotes
• diploidy, sexual reproduction
• multicellularity
  
  • red algae
  • aquatic organisms colonise land
• first short embryo-bearing plants (mosses) and animals (arthropods) on land
• first lichens and mycorrhizal-like fungi

Question 2

If one species has lost the ability to survive without its partner, it is known as

Answer 2

obligate mutualism

Question 2

Fungus-Plant Mutualisms

Answer 2

○ Most plants in their natural ecosystems have fungal endophytes
Live entirely within the tissue, often living in the place between the cells without causing noticeable harm
Action is not limited to the roots (different from mycorrhizal fungi) and the interaction is diverse
Most are ascomycetes

Question 2

the general term for an infection caused by a fungal parasite

Answer 2

mycosis

Question 2

• Soredia

Answer 2

algal cells surrounded by fungal hyphae that can break off

Question 2

amensalism

Answer 2

one is not affected, the other is negatively affected

Question 2

how do lichen get their nutrients

Answer 2

from rainwater or melting snow

Question 3

What symbiosis has a sandwich structure

Answer 3

lichen

Question 4

Mycorrhizzae

Answer 4

Fungus-root symbiosis

Increase water uptake for plant, fungus receives carbon

Question 5

endo vs ecto mycorrhizae

Answer 5

endo - form tree-link structures within plant hosts, 80% of vascular plant species, maximizes carbon from plant to fungus

ecto - grow around plant host cells and form a sheath, produce proteases to break down proteins

both important extensions of the plant-root system AND important for decomp and nutirent cyclign

Question 6

Derived Traits of Plants

Answer 6

The cuticle: helps against drying out

Stomata: support photosynthesis by allowing gas exchange

Early plants lacked roots
For nutrients formed a symbiosis with fungi - mycorrhizae

Question 6

summarize the potential importance of lichens and mycorrhizae to the evolution of land plants

Answer 6

probably essential for ancestral plants to colonise land
fungi help supply water and nutrients for plant acquisition
diversity begets diversity
fundamental in the functioning of terrestrial ecosystems

Question 6

discuss the principal new traits that ancestral open water algae had to evolve to successfully grow, survive and reproduce in the shoreline environment, and then in the terrestrial environment

Answer 6

multicellular form with thallus (shoot) and anchoring organs (roots)

specialized meristems for directed localized growth in a large multicellular organism

cell walls for structural support (cellulose)

they had to adapt to more selection pressures on land that were not in the aquatic habitat

mucilage to resist desiccation
resistant to drying out
did this though evolving to have cuticles and waxes to reduce water loss from cells

conducting tissues

Question 6

advantages and disadvantages for plants in aquatic vs terrestrial environments

Answer 6

aquatic
- good the be small, flat and buoyant
-lots of available nutrients, and water takes away waste
-not good for larger plants in dense environments

terrestrial
-good for tall plants in dense environments
-competition for light
-bad for small plants in dense environments
-okay for small plants in sparse environments

Question 7

plants evolved from

Answer 7

green algae
○ Multicellularity, photosynthetic pigments, cell walls composed of cellulose
○ Closest living relative

Question 7

what was essential for ancestral plants to colonize land

Answer 7

lichens and mycorrhizae

lichens helped with making soil organic matter that stored nutrients

mychorrhizae helped with water uptake and the development of the plant body

Question 8

all land plants (embryophytes) have___

Answer 8

multicellular dependent embryos
- diploid embryo is retained within the female gametophyte
- Nutrients are transferred from parent to embryo through placental transfer cells

Question 8

• describe what early land plants looked like

Answer 8

○ simple structures with reproductive tips
○ no cellulose
○ environments were open with lots of light and oxygen available

Question 8

discuss the principal new traits that early land plant species has to evolve to successfully grow, survive and reproduce while competing with other land plant species for light, soil water and nutrients, and new habitat for colonization

Answer 8

root systems
vascular tissue
cuticle and stomata
reproductive adaptations
height and architecture
secondary meiosis
symbiotic associations

Question 9

Which evolutionary selective forces have been most important in generating such structural and functional diversity in the Kingdom Plantae?

Answer 9

Niche adaptation
○ Differing abiotic environmental features spatially and temporally
○ Differing biotic pressures such as inter- and intra- specific competition (exacerbated by immobility), herbivory, pathogens, symbionts

Resource acquisition
○ Belowground: water and nutrient acquisition
○ Aboveground: enhancing light availability (with crowded neighbours)n that promoted traits for growing tall

Dispersal: Transport over land

Question 10

a bryophytes life cycle is dominated by which stage?

Answer 10

the gametophyte stage

Question 10

Bryophytes: explain their principal biological features, and the typical niches that they occupy

Answer 10

-mosses require moisture
-are non-vascular
-short stature, soft-tissued
They like to stay within the boundary layer (slows down wind, high CO2, moist)
-life cycle is dominated by the gametophyte stage

-has alternation of generations as sexual life cycle
sporophyte is a diploid multicellular structure, grows up from the female gametophyte
gametophyte is a haploid multicellular structure
there has to be water for the sperm to be able to swim to the egg
no water = no fertilization

separate male and female gametophyte plants

Question 10

○ outline the general phylogeny of the bryophytes, including relative species richness and evolutionary trends

Answer 10

are non-vascular

evolved from algae first

common ancestor between liverworts and mosses evolved stomates
□ stomates are pores in the leaves to stop water from going out and allow gasses to come in (control of gasses in and loss of moisture out)

Question 10

the names of the male and female gametophytes in mosses

Answer 10

Male: Antheridia
Female: archegonia
- zygote develops within the archegonium

Question 11

bryophtye spores are encased in

Answer 11

sporopollenin

Question 11

Evolution of Leaves

Answer 11

Increase surface area for photosynthesis

Microphylls are small spine shaped, supported by a single strand of vascular tissue
Present in lycophytes (oldest lineage of vascular plants)

Megaphyll - larger more advanced leaf with branched vascular system

Question 12

describe the asexual and sexual reproduction life cycle of a typical fern

Answer 12

are bisexual
have both male and female gametes and can self
these plants produce sexually
sporophyte is greatly enhanced
sporophyte has evolved sporophylls that produce multiple sporangia per original gametophyte plant

Question 12

pteridophytes: principal novel features, and the evolutionary selection pressures that would have generated them

Answer 12

can transport water vertically, giving rise to height
first plants to grow tall

primitive vascular tissue, stem branching, roots and modified leaves that bear sporangia

sporophyte - dominant phase of life cycle
-have multiple sporangia per original gametophyte