1. The reproductive process in the lower plants (mosses, liverworts, and ferns) can be said to be analogous to thereproductive process in the amphibians. Explain. 2. Just as a look at embryonic development has helped to demonstrate the close relationship between chordatesand echinoderms, a look at embryonic development also is key to understanding the relationship between greenalgae and bryophytes. Explain. 3. The fossil record provides little information about ancient mosses. Do your think that nonvascular plants couldever have been large-tree-sized plants? Provide evidence from your investigations to support your answer. 4. Fern antheridia release sperm that then swim toward archegonia in a watery film. The archegonia release a fluidcontaining chemicals that attract the sperm. This is an example of chemotaxis, the movement of cells ororganisms in response to a chemical. What is the significance of chemotaxis to fern (and moss) reproduction? 5. German scientists studied air pollution from heavy metals (cadmium, copper, lead, nickel, and zinc) by analyzingthe concentration of these metals in moss samples. They compared mosses collected between 1845 and 1974,which were preserved as herbarium specimens, with mosses collected in 19991. In general, the 1991 mosses hadlower heavy metal concentrations. These results were attributed to increased air pollution controls. Based onyour knowledge of the structure of the moss gametophyte, can you suggest one or more reasons why mosses areparticularly useful indicators of air pollution? 6. Evidence indicates that the evolution of vascular tissue coincided with a five fold drop in atmospheric CO2 levelsduring the Carboniferous period, causing global cooling that resulted in widespread glacier formation. What is apossible explanation for this? Solution 1. Sexual reproduction in lower plants is carried out through motile sperm with flagella. Water is required to facilitate reproduction.Haploid gametes are produced by anthridia and archigonia by mitosis. The sperm released from the anthredia responds to the chemicals released by ripe archigonia and swim to them in a fim of water and fertilize the egg cell thus producing zygote.The zygote divides by mitotic division and grows into a sporophyte that is a diploid. in case of amphibians also external ferilization takes place.The male and female that are copulating relese their sperm and egg at the same time. A tadpole that is a solely aquatic larval stage emerges from the egg after the egg is fertilized. 2. In both algae and bryophytes,plant body is thalloid and undifferentiated.Gametophytic generation is the prominent phase in the life cycle in both groups.Both groups are autotrophic in nutrition.In both the major photoynthetic pigments are Chlorophl a,b, and carotenes.Vascular tissue is absent in both groups.Cellulose is chief constituent of cell wall in both groups.Alternation of generation is present in both groups. 3. They could only have been mat forming on .

1. 1. The reproductive process in the lower plants (mosses, liverworts, and ferns) can be said to be
analogous to thereproductive process in the amphibians. Explain.
2. Just as a look at embryonic development has helped to demonstrate the close relationship
between chordatesand echinoderms, a look at embryonic development also is key to
understanding the relationship between greenalgae and bryophytes. Explain.
3. The fossil record provides little information about ancient mosses. Do your think that
nonvascular plants couldever have been large-tree-sized plants? Provide evidence from your
investigations to support your answer.
4. Fern antheridia release sperm that then swim toward archegonia in a watery film. The
archegonia release a fluidcontaining chemicals that attract the sperm. This is an example of
chemotaxis, the movement of cells ororganisms in response to a chemical. What is the
significance of chemotaxis to fern (and moss) reproduction?
5. German scientists studied air pollution from heavy metals (cadmium, copper, lead, nickel,
and zinc) by analyzingthe concentration of these metals in moss samples. They compared mosses
collected between 1845 and 1974,which were preserved as herbarium specimens, with mosses
collected in 19991. In general, the 1991 mosses hadlower heavy metal concentrations. These
results were attributed to increased air pollution controls. Based onyour knowledge of the
structure of the moss gametophyte, can you suggest one or more reasons why mosses
areparticularly useful indicators of air pollution?
6. Evidence indicates that the evolution of vascular tissue coincided with a five fold drop in
atmospheric CO2 levelsduring the Carboniferous period, causing global cooling that resulted in
widespread glacier formation. What is apossible explanation for this?
Solution
1. Sexual reproduction in lower plants is carried out through motile sperm with flagella. Water is
required to facilitate reproduction.Haploid gametes are produced by anthridia and archigonia by
mitosis. The sperm released from the anthredia responds to the chemicals released by ripe
archigonia and swim to them in a fim of water and fertilize the egg cell thus producing
zygote.The zygote divides by mitotic division and grows into a sporophyte that is a diploid.

2. in case of amphibians also external ferilization takes place.The male and female that are
copulating relese their sperm and egg at the same time. A tadpole that is a solely aquatic larval
stage emerges from the egg after the egg is fertilized.
2. In both algae and bryophytes,plant body is thalloid and undifferentiated.Gametophytic
generation is the prominent phase in the life cycle in both groups.Both groups are autotrophic in
nutrition.In both the major photoynthetic pigments are Chlorophl a,b, and carotenes.Vascular
tissue is absent in both groups.Cellulose is chief constituent of cell wall in both
groups.Alternation of generation is present in both groups.
3. They could only have been mat forming on land.With no way to conduct and share water
soluble nutrients, they had to rely on every area being in contact with a water source. While the
outer cells absorb water inner caels ust wat till water moves passively to reach them.Their state
of hydration is dependent on environment,they cannot control it.This limits the thickness the mat
can achieve.
4. Chemotaxis is important in fertilzation of lower plants that depend on swmming sperm to find
the egg. Sperms are attrachted to a liquid that is discharged from the necks of receptive
archigonia.This is an example of positive chemotaxis.
5. since mosses lack roots ,surface absorption of rainwater is the only means by which they
obtain the vital nutrients present in the rainwater. Mosses lack protective mechanisms by whch
they can can block out pollutants present in rain water.Mosses lack waxy cuticle.This rapid and
diresct absorption is detrimental when atmospheric moisture is laden with pollutants. Therefore
they are used for monitoring air pollution.