lecture 2

Question 1

what is considered a modern tree?

Answer 1

• woody perennial plant
• with secondary growth
• elongated stem (trunk) supporting branches and leaves

Question 2

what is secondary growth?

Answer 2

thickening of stems/ roots through vascular cambium and cork cambium; creates rings

Question 3

what is a perennial plant?

Answer 3

one that lives for more than 2 years returning and regrowing year after year from its roots

Question 4

what are the 3 example of non-modern trees and why are they considered non-modern + the overall reasoning

Answer 4

i. Bamboos (monocots): perennial, but no secondary growth
ii. Palms and bananas (monocots): perennial, but no secondary growth
iii. Tree ferns: perennial, but trunk is not wood, no secondary growth

overall, these species lack true wood or secondary thickening achieving height through other structural strategies like bundled vascular tissue or root/ stem density

Question 5

what type of clade within the tree evolution phylogeny are plants? trees?

Answer 5

Plants are monophyletic group (all come from common ancestor)

Trees are polyphyletic (evolved multiple times independently in different plant lineages)

Question 6

why are trees polyphyletic and what type of evolution caused this to happen?

Answer 6

the woody tree-like form has evolved independently multiple times in different lineages of plants rather than arising from a single common ancestor that was itself a tree.

it has evolved convergently

Question 7

what is convergent evolution?

Answer 7

the independent evolution of similar features in species of different periods in time creating analogous structures that have similar form or function but were not present in the last common ancestor of those groups

Question 8

plants descended from what origin?

Answer 8

from a eukaryotic ancestor + a cyanobacteria via primary endosymbiosis

Question 9

what is endosymbiosis?

Answer 9

one cell engulfing another to produce, over time, a coevolved relationship in which neither cell could survive alone

Eg. Chloroplasts of red and green algae are derived from the engulfment of a photosynthetic cyanobacterium by an early prokaryote

Question 10

did the evolution of photosynthesis evolve in bacteria through endosymbiosis? if yes/no why?

Answer 10

No, photosynthesis was not evolved in bacteria through endosymbiosis; rather, photosynthesis first evolved in bacteria, specifically in a photosynthetic cyanobacterium, and was later acquired by a non-photosynthetic eukaryotic cell (a protist) through the endosymbiosis of these cyanobacteria. This process allowed the cyanobacteria to become chloroplasts within the host eukaryotic cell, leading to the evolution of photosynthetic eukaryotes like plants and algae.

Question 11

are some of the “plant” genes that derived from the ancestral bacteria more like bacterial genes or eukaryotes genes?

Answer 11

based on the explanation answered from the question above….
some plant genes are more like bacterial genes that the genes of other eukaryotes

Question 12

topic: transition to land plants.
Terrestrial macro-flora evolved once from one lineage of what? then what happened after and why?

Answer 12

of green algae (likely freshwater). Then innovation happened in response to several factors.
Living on land meant losing the “safety net” of water. Every feature of land plants evolved to deal with challenges like desiccation, gravity, and reproduction away from water

Question 13

what is embryophytes?

Answer 13

land plants

Question 14

Then innovation happened in response to several factors (aka. plants had to adapt to harsh environments) like the…

Answer 14

• access to light and to water
• reproduction efficiency (aka. Efficient mating)
• access to more habitats
• mutualism (with fungi, pollinators, etc. — need to start establishing collaboration with other organisms in the environment)
• protection from abiotic stresses (excessive light, drought —need to access underground water for example) and from biotic stresses (competitors, herbivores, pathogens)

Question 15

what is Apomorphies?

Answer 15

Derived trait: An apomorphy is a new trait that differs from the ancestral version

Question 16

what are the 3 major innovations (Apomorphies) in early land plants in response to these new stresses?

Answer 16

1. alternation of generation
2. evolution of parenchyma tissue
3. evolution of cutin

Question 17

major innovations (Apomorphies) in early land plants:
(a) explain the “alternation of generation” innovation in early land plants

Answer 17

goodnotes

Question 18

major innovations (Apomorphies) in early land plants:
(b) explain the “evolution of parenchyma tissue” innovation in early land plants

Answer 18

goodnotes

Question 19

major innovations (Apomorphies) in early land plants:
(c) explain the “evolution of cutin” innovation in early land plants

Answer 19

goodnotes

Question 20

what are the major innovations (apomorphies) in vascular plants?

Answer 20

goodnotes

Question 21

what are the major innovations (apomorphies) in seed plants?

Answer 21

i. Secondary growth: wider trunks, concentric rings

ii. Evolution of seeds: embryo protection, dispersal, dormancy

iii. Pollination: replacing water-dependent fertilization

Question 22

major innovations (apomorphies) in seed plants:
what is a seed?

Answer 22

Seeds contain a dormant, embryo (undeveloped plant) surrounded by a protective coat along with stored food reserves.
When environmental conditions become favourable the seed germinates using its stored resources to begin growth and develop into a seedling.
This dormancy mechanism allows plants to survive unfavourable conditions and disperse over time

Question 23

major innovations (apomorphies) in seed plants:
(ai) explain the secondary growth of trees — growing taller and wider

Answer 23

1. Involved vascular cambium producing secondary xylem (wood) and phloem
2. Create concentric growth rings
3. Trees grow taller and wider

Question 24

major innovations (apomorphies) in seed plants:
(aii) what is Archaeopteris?

Answer 24

the first modern trees
a. Progymnosperm tree with fern-like leaves
b. Deeper rooting system
c. Long-lived branches
d. Real leaves
e. Growth both upwards and outwards

Considered modern because of the concentric tree rings and secondary growth pattern (and the ability to create cambium)

Question 25

major innovations (apomorphies) in seed plants: (b) The evolution of seeds enabled seed plants to extend their habitats. (seeds = game changing innovation for land plants). What are the 4 key functions that plant seeds are doing? seeds facilitated plants dispersal by....

Answer 25

i. Seeds protect the embryo (seed coat protects from desiccation, physical damage and predators) ii. Seeds are the units of dispersal (wind, water, animals. different groups of plants have specialized seed morphology) iii. Seeds have dormancy (wait for the ideal germination conditions) iv. Seeds provide nutrients (to the embryo during early germination time. stored food helps seedlings establish easier in a new habitat)

Question 26

major innovations (apomorphies) in seed plants: what are the 3 diversification of seed plants? define all three.

Answer 26

Pteridosperms A paraphyletic group of fossil plants that had fernlike foliage but produced seeds (aka. were the earliest seed plants to appear in the fossil record but are now extinct. They had fern-like leaves but reproduced via seeds) - Medullosa is a well-known example of a seed fern Gymnosperms Dominated the landscape before angiosperms. (seed-bearing plant in which the ovule is borne on an open scale, not embedded in an ovary) aka. Have “naked seeds” that develop in cones and are exposed Angiosperms Appeared later becoming the dominant group of land plants today. (flowering plants, seeds enclosed in a fruit which is a structure derived from the ovary) aka. “flowering plants”; seeds enclosed within a protective fruit that develops from the ovary of a flower so.... pteridosperms (seed ferns) are an extinct group of early seed plants, and the primary diversification of seed plants involved the evolution and spread of both gymnosperms and angiosperms

Question 27

what are the 3 main orders plus another group of gymnosperms? what is the key trait?

Answer 27

1. Cycadaleas 2. Ginkgoales 3. Pinales 4. Plus the group Gnetophyte (phylogenetic position debated but in most phylogenetic trees they are a sister group of pinales) Key trait: sperm cells are non-flagellated sperm in conifers and gnetophytes

Question 28

Gymnosperms lost the tail/ flagella = lost the ability to swim which led to the evolution of what? explain.

Answer 28

Pollination droplet (PD) the evolution of the PD occurred after the loss of flagella in many gymnosperm lineages, serving as an alternative mechanism for pollen capture and delivery, replacing the need for motile sperm to swim to the egg and facilitating fertilization independently of liquid water environments

Question 29

What is pollination droplet (PD)?

Answer 29

a liquid, sugary secretion produced by the ovules of gymnosperms (like conifers and ginkgoes) that protrudes from the micropyle, or opening of the ovule serving as a landing site for airborne pollen grains. After pollen lands on the drop, it gets immersed and, as the drop is withdrawn into the ovule so in short a. Secreted from the micropyle of ovules b. Captures pollen, transports into ovule c. Functions as a landing/ germination medium there is a figure of the PD formation: i. A: droplet exuding from micropyle during pollination ii. B: microscopic view (200 μm scale) iii. Essential adaptation because sperm lost motility; the drop “pulls” pollen inside

Question 30

Gymnosperm: 1. Gingko biloba (order: Ginkgoales)

Answer 30

doc and slides

Question 31

gymnosperm: 2. Conifers (most derived gymnosperms): i. what are the general characteristics?

Answer 31

i. Most are evergreen ii. Needle-like leaves: thin, dark green (adapted for low light, weak sun, and conserving water) iii. Produce resin: protects against insects, pathogens, frost (acts as antifreeze) iv. Wind-pollinated, seeds develop in cones (strobili) v. Dominate taiga forests of Northern Hemisphere

Question 32

gymnosperm: 2. Conifers (most derived gymnosperms): ii. what are the conifer structures? explain briefly each

Answer 32

i. Resin canals: lined with parenchyma cells; secrete resin (terpenes + resin acids) ii. Needles: minimize water loss, stay year-round iii. Male cones (microsporangia): produce pollen in sacs; release via drying → wind dispersal iv. Female cones (ovulate strobili): house ovules, produce pollination droplets, seeds develop after fertilization.

Question 33

gymnosperm: 2. Conifers (most derived gymnosperms): iii) some figures iv) what is conifer's apomorphy? first why, what, and further explain what the 2 adaptations were.

Answer 33

why: loss of sperm cell momtility where unlike many other plants, conifer sperm cells do not have flagella and are not motile what: Pollination droplet (in conifers). gymnosperms have a pollination droplet, a secretion from the ovule that helps transport pollen grains to the micropyle (the opening of the ovule) -- visual figure in pg 60. i. Ovule secretes sticky droplet from micropyle. ii. Pollen lands, hydrates, is pulled inside ovule. iii. Critical adaptation for fertilization without water adaptation: loss of sperm motility. i) generative cell: divides to form 2 sperm cells ii) tube cell: forms a tube to deliver pollen to ovule iii) prothallial cells: remnants from gametophyte development iv) air sacs/ sacci: provide buoyancy for pollen (pg 61 for visual figure of the anatomy) adaptation: pollination droplet. a liquid secretion produced by the ovule and protruding from the micropyle serves as a landing site and germination medium for pollen grains, crucial for their capture, hydration, and transport into the ovule. (pg 62 for visual figure of the anatomy)

Question 34

gymnosperm: 2. Conifers (most derived gymnosperms): v) idk talk about conifer distribution and evolution

Answer 34

pg 64-66 for answers.... waky taky answers from doc: i. Widespread across Northern Hemisphere; also in mountains southwards. ii. Disjunct distribution today due to: Mass extinctions and Long-distance migrations (confirmed by molecular clock, after Pangaea split). iii. figures: Map of Pangaea with migration routes across continents (via land bridges like Bering Land Bridge, North Atlantic Land Bridge)