Seed Plants - Ch. 26

Question 1

male gametophytes

Answer 1

pollen grains, dispersed by wind or pollinaters, no need for water

Question 2

female gametophytes

Answer 2

develop within the ovule, enclosed within the diploid sporophyte tissue in angiosperms

Question 3

gymnosperms

Answer 3

plants with “naked seeds”
all lack flowers and fruits of angiosperms, all have an exposed ovule
can be divided into 4 groups: coniferophytes, cycadophytes, gnetophytes, and ginkgophytes

Question 4

conifers (phylum coniferophyta)

Answer 4

most familar gymnosperm phylum
includes: pines, spruces, firs, cedars, etc.
found in colder and drier regions
source of important products like timber, paper, resin, or taxol

Question 5

pines (conifer)

Answer 5

more than 100 species in the N. hemisphere
produce tough needle like leaves in clusters, leaves have thick cuticles and recessed stomata to prevent water loss, leaves have canals with resin to deter insect and fungal attacks

Question 6

pine reproduction

Answer 6

• male gametophytes (pollen grains) develop from microspores in male cones by meiosis.
• female pine cones form on the upper branches of the same tree. the female cones are larger and have woody scales, 2 ovules develop on each scale, each contains a megasporangium that will become a female gametophyte.
• female cones usually take 2 seasons or more to mature.
• during the first spring, pollen grains drift down between the open scales.
• a year later, female gametophyte matures and the pollen tube grows. the mature male gametophyte will have 2 sperms.
• 15 months after pollination, pollen tube reaches the archegonium and discharges contents to produce a zygote.

Question 7

cycads (phylum cycadophyta)

Answer 7

slow growing gymnosperm of tropical and subtropical regions. sporophytes resemble palm trees, and has the largest sperm of all organisms, thrive in mild climates, can be pollinated by beetles or wind

Question 8

gnetophytes (phylum gnetophyta)

Answer 8

only gymnosperm with vessels in their xylem, has three genera: welwitschia, ephedra, and gnetum

Question 9

ginkgophytes (phylum ginkgophyta)

Answer 9

only one species remains: ginkgo biloba, has flagellated sperm, dioecious (male and female reproductive structures form on different trees)

Question 10

angiosperms

Answer 10

flowering plants, ovules are enclosed in diploid tissues at the time of pollination, carpal, a modified leaf that covers seeds develop into fruit, fruits, in flowering plants, add a layer of protection to seeds that attract animals that assist in seed dispersal, expanding the potential range of species
originated 145-208 mya

Question 11

flower morphology

Answer 11

modified stems bearing modified leaves, primordium develops into a bud at the end of stalk called the pedicel, the pedicel expands at the tip to form a receptacle, to which other parts attach. flower parts are organized in circles called whorls

Question 12

flower whorls

Answer 12

outermost whorl = sepals
second whorls = petals
third whorls = stamens 
innermost whorl = gynoecium
-consists of one or more carpels and house the female gametophyte

Question 13

carpel

Answer 13

has three major regions:

• ovary = the swollen base containing ovules, later develops into a fruit
• stigma = tip where pollen lands
• style = neck or stalk

Question 14

pollination

Answer 14

mechanical transfer of pollen from anther to stigma, may or may not be followed by fertilization, pollen grains develop a pollen tube that is guided to an embryo sac

Question 15

advantages to life on land

Answer 15

sunlight is abundant, carbon dioxide is more readily available, and land plants evolved before land animals

Question 16

advantages to seeds

Answer 16

have a protective coat, prevents desiccation and no need for constant water supply, seeds can remain in a state of dormancy

Question 17

when did flowering plants first appear?

Answer 17

125 mya in the lower cretaceous period and diversified about 200 mya

Question 18

what did angiosperms originate from?

Answer 18

no consensus, but may have originated from small, woody bushes or tropical grasses, not derived from gymnosperms, they are a sister clade

Question 19

characteristics of gymnosperms

Answer 19

paraphyletic group (may not have derived from a single ancestor)
naked seeds, separate male and female gametophytes, pollen cones and ovulate cones, pollination by wind or insects, tracheids, alternation of generation, heterosporous,

Question 20

do gymnosperms have ovaries?

Answer 20

no, they are partially sheltered by modified leaves called sporophylls.
a layer of sporophyte tissue that surrounds the megasporangium and later the embryo

Question 21

lifecycle of a conifer

Answer 21

• male and female develop on different strobili
• in male cones, the microsporophyte undergoes meiosis and give rise to male gametophytes (pollen)
• a pollen tube develops slowly and the pollen grain will produce 2 haploid sperm by mitosis
• at fertilization, the haploid sperm will unite with the egg cell
• female cones, contains two ovules per scale
• each ovule has a narrow passage that opens near the base of the sporophyll, which is where the pollen tube will grow
• the megaspore will undergo meiosis, and a single cell will become a female gametophyte
• as the female gametophyte develops, a sticky pollination drop traps pollen so a pollen tube will grow.
• the sperm and egg will fuse to make a zygote

Question 22

lifecycle of an angiosperm

Answer 22

• inside the anther’s microsporangia, male sporophytes divide by mitosis to make pollen grains. There are two cells, one will divide to produce 2 sperm and the other will make the pollen tube
• the ovule, sheltered within the ovary, contains the megasporangium
• within the megasporangium, the megasporocyte undergoes meiosis to produce 4 haploid megaspores. there are 1 big and 3 smalls and only the big survives
• the large megaspore divdes 3x to produce 8 nuclei. 3 cells at one pole become an egg and 2 synergids. the three 3 cells at the opposite pole become antipodal cells. the remaining 2 will be at the center of the cell and become the endosperm.
• one sperm and egg will unite to form a diploid zygote
• the other sperm with fuse with the two cells to make an endosperm, which is the food source for the egg
• the zygote develops into an embryo with a radide (small root), and 1-2 cotyledons

Question 23

what are the two categories of fruit?

Answer 23

fleshy (berries, peaches, apples, etc.) and dry (rice, wheat, nuts)

Question 24

what are the three groups of angiosperms?

Answer 24

basal, monocots, and eudicots

Question 25

basal angiosperms

Answer 25

• the magnoliidae (magnolias, laurels, peppers)
• the whorls of magnolias is sepals and petals are undifferentiated and called tepals
• produce cone-shape receptacle fruit

Question 26

monocots

Answer 26

• primarily identified by the presence of a single cotyledon seedling
• veins run parallel on length of the leaf, flowers arranged in 3-6 fold symmetry, true woody tissues is rarely found
• first pollen producing angiosperm was probably a monocot
• vascular tissue is not organized in the stem but is in the roots
• no major tap root, multiple fibrous roots

Question 27

eudicots

Answer 27

• true dicots
• characterized by 2 cotyledons
• veins form a network in leaves
• flowers come in 4,5, or more whorls
• can be herbaceous or produce woody tissue
• root system is anchored by 1 main root
• comprise 2/3 of all flowering plants