Lecture 20: Seed Plants, Gymnosperms and Angiosperms (Midterm III)

Question 1

What are two key adaptations that allowed plants to inhabit terrestrial ecosystems?

Answer 1

seeds and pollen grains

Question 2

what is a seed

Answer 2

consists of an embryo (entire individual) and nutrients surrounded by a protective coat

Question 3

4 common characteristics among seed plants

Answer 3

heterospory, reduced gametophytes, ovules, and pollen

Question 4

1. heterospory (seed plants)

Answer 4

• ancestors of seed plants were likely homosporous, while seed plants are heterosporous
• sees plants produce two different spore sizes: microspores –> males, megaspores –> female gametophytes
• Megasporangia (2n) –> megaspores (n) & microsporangia (2n) –> microspores (n)

Question 5

2. reduced gametophytes (seed plants)

Answer 5

• provides protection as the gametophytes of seed plants develop within walls of spores retained within tissues of the parent sporophyte

Question 6

3. ovules (seed plants)

Answer 6

• integument + megasporangium + megaspore or egg
• gymnosperm megasporangia have one integument
• angiosperm with two integuments

Question 7

4. pollen (seed plants)

Answer 7

• microspores develop within **pollen grains **
• pollination
• **pollen eliminates the need for a film of water and can be dispersed great distances by air or animals **
• if a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule

Question 8

explain seeds and their development

Answer 8

• a seed develops from the whole ovule
• a seed is a sporophyte embryo, along with its food supply, packaged in a protective coat

Question 9

evolutionary advantage of seeds

Answer 9

• may remain dormant for days to years, until conditions are favorable for germination
• may be **transported long distances ** by wind or animals

Question 10

Gymnosperms and their 4 phyla

Answer 10

• they have “naked” seeds not enclosed by ovaries
  1. cycadophyta (cycads)
  2. gingkophyta (ginkgo biloba)
  3. gnetophyta ( 3 genera: Gnetum, Ephedra, Welwitschia)
  4. Coniferophyta (conifers, such as pine, fir, or redwood)

Question 11

Ginkgophyta

Answer 11

• ## high tolerance to air pollution & a popular ornamental tree

Question 12

Cycadophyta

Answer 12

• 200 species
• palm-like
• seeds produced large cones
• thrived during the Mesozoic, relatively few species exist today

Question 13

Gnetophyta

Answer 13

• diverse
• ## species vary in appearance, some tropical others live in deserts

Question 14

Coniferophyta

Answer 14

• 550 species, important ecologically and economically
• needle-shaped leaves
• mostly evergreen
• largest forests on Earth are mostly conifers
• largest organism: giant sequoia
• tallest organism: coast redwood
• oldest non-clonal organism: bristlecone pine

Question 15

3 key features of the gymnosperm life cycle

Answer 15

a. dominance of sporophyte generation
b. development of seeds from fertilized ovules
c. transfer of sperm to ovules by pollen

Question 16

life cycle of a pine

Answer 16

1. familar pine tree is the sporophyte and produced sporangia in male & female cones
2. small cones produce microspores within pollen grains; microspore will develop into male gametophyte
3. familar large cones contain ovules, which produce megaspores that develop into female gametophytes

Question 17

over time, what two adaptations occur in plants (angiosperms)

Answer 17

1. decreasing reliance on liquid water for fertilization
2. increasing dominance of sporophyte generation

Question 18

what are angiosperms

Answer 18

• seed plants with reproductive structures called flowers & fruits
• most widespread & diverse of all plants

Question 19

3 characteristics of angiosperms

Answer 19

1. all classified in a single phylum, Anthophyta
2. the flower is a unique structure to Angiosperms specialized for sexual reproduction
3. many species are pollinated by animals, while some are wind-pollinated, others are selfing

Question 20

four types of leaves on flowers

Answer 20

1. sepals (calyx) – cover immature flower bud
2. petals: (corolla) - brightly colored & attract animals to serve as **pollinators **
3. stamens: microsporophylls; make microspores which make male gametophytes (pollen) within the anthers
4. carpels: megasporophylls; make megagaspores, female gametophytes, and seeds

Question 21

fruits and their characteristics

Answer 21

1. consists of a mature ovary but can also include other flower parts
2. fruits protect seeds and aid in their dispersal
3. mature fruits can be either fleshy or dry
4. fruits help disperse seeds
5. seeds can be carried by wind, water or animals

Question 22

Angiosperm Life Cycle

Answer 22

1. flower of sporophyte is composed of both male and female structures
2. male gametophytes are contained within pollen grains produced by microsporangia of **anthers **
3. female gametophyte/**embryo sac **develops within an ovule contained within an ovary at the base of a stigma
4. flowers have mechanisms for cross-pollination between flowers from diff plants from the same species

Question 23

3 unique reasons for angiosperms success

Answer 23

1. rapid life cycle
2. symbioses
   - pollination: efficient targeted delivery
   - fruit & suit dispersal: for transport
   - mycorrihizae (interactions between soil fungi & roots)
3. more effective vascular tissues - vessel elements, sieve tube members

Question 24

two main types of angiosperms

Answer 24

monocots (one cotyledon) & eudicots (two cotyledons)

Question 25

monocots

Answer 25

a. single cotyledon (embryo starts with one leaf
b. parallel leaf vasculature
c. complex arrangement of vascular bundles
d. fibrous roots
e. flowers in multiples of 3
f. ex ( major grains, lilies, orchids, yuccas, palms, grasses)

Question 26

eudicots

Answer 26

a. double cotyledon - starts with two leaves
b. leaf vasculature tends to be a network **
c. vascular bundles in stem arranged in a ** ring
d. central large taproot
e. flowers in multiples of 4 or 5
f. ex ( legumes(peas), broad-leafed trees (oaks, maples), roses; most human crops