Lab 4: Plants part 2: the plant development and the C-fern life cycle

Question 1

what organisms have land plants evolved from?

Answer 1

they evolved from ancestral green algae

Question 2

What are the three major groups of plants?

Answer 2

1. Non-vascular plants
2. Seedless vascular plants
3. vascular seed plants

Question 3

What species make up the non-vascular plants? What are they also called?

Answer 3

Liverworts, mosses and hornworts make up the non-vascular plants, they are also called bryophytes

Question 4

What species make up the seedless vascular plants?

Answer 4

Lycophytes (club mosses..etc..), and pterophytes (ferns..etcs..) main one is ferns

Question 5

What species make up the vascular seed plants?

Answer 5

Gymnosperms and angiosperms

Question 6

What is the life style of the plants typically called and what are the two distinct phases that occur?

Answer 6

it is called alternation of generations. and the two distinct phases that occur is through the events of meiosis and fertilization

Question 7

What are spores?

Answer 7

spores are single cells that germinate and develop via mitosis under appropriate conditions into multicellular plants that produce the sex cells or gametes by mitosis

Question 8

What are gametophytes?

Answer 8

the haploid phase. they are the spores that form into the compartment where the male and female gametes (spermatozoids and egg cells) are carried and the site of fertilizaiton

Question 9

What is the sporophyte?

Answer 9

it is the diploid stage of the cycle, where fertilization grows a zygote

Question 10

Which types of plants are sporophyte dominant?

Answer 10

ferns and seed plants

Question 11

What is so special about the relationship between ferns and their gametophytes?

Answer 11

in ferns, the sporophyte and gametophyte are independent of one another

Question 12

What is homospory and which plants display it?

Answer 12

homospory is that on kind of spore develops in the sporangia and it is bisexual (not a male or female) and it is usually apparent in mosses and ferns

Question 13

What is heterospory?

Answer 13

It is when two types of spores develop like a male and female and it develops in two different types of sporangia i.e. megasporangia and microsporangia

Question 14

What type of species are we doing the gametophytic density and sex expression exercise on?

Answer 14

doing it on the ceratopteris sp. that we sowed in lab 1 with the dilutions

Question 15

What are some characteristics of the ceraptopsis sp.?

Answer 15

it is a homorsporous fern that has two distinct phases in the life cycle. It is a simple haploid gametophyte and a more complex diploid sporophyte that has leaves, stems and roots with vascular tissue

Question 16

How did the spores in lab germinate and develop?

Answer 16

They germinated and developed in a mature haploid gametophyte via mitotic cell division

Question 17

What did the gametophyte consist of?

Answer 17

small thallus with rhizoids (for structural support), and sexual organs known as antheridia and archegonia.

Question 18

What is the antheridia?

Answer 18

it is the area of the gametophyte that produces sperm

Question 19

what is the archegonia?

Answer 19

it is the area of the gametophyte that produces eggs

Question 20

How does the fern fertilize?

Answer 20

only in the presence of water. The flagellated sperm are released from the anthredia and start to swim to seek a receptive egg. Water causes the neck of the archegonium to open an release a chemical that causes the sperm to swarm at the neck of the opening.
- sperm then swim down the neck and fertilize the egg.
This results in the diploid zygote forming and undergoing mitotic cell dicison to from the embryo which develops in a new diploid sporophyte

Question 21

What are the two different types of gametophytes that are developed from a fern spore?

Answer 21

1. the hermaphroditic gametophytes which have both the archegonia and anthredia –> they are larger and don’t stop growing
2. The male gametophytes which only contain anthredia and are very tiny

Question 22

How is sexual differentiation controlled in the fern?

Answer 22

it is controlled via a pheromone-like substance called the antheridiogen Ace, which is secreted by the gametophytes.

Question 23

What is ACe, and what does it do?

Answer 23

it is a pheromone that is released to trigger the growth of male gametophytes. It is typically released by the hermaphroditic gametophytes when there are too many of them being produces, so that it can add diversity in the genes.

Question 24

Why is ACe important?

Answer 24

because in the absence of it, the plant produces only hermaphrodites with both archegonia and a few anthredia.
The hermpahroditic plants have a meristematic region that presented indeterminate growth (non-stop growth) until its fertilized and because it is a big gametophyte it obviously takes more energy for the plant to make more. So the hermaphrodites release ACe to allow more male gametophytes to be produced because they are smaller, determinate and get released in larger amounts to preserve energy

Question 25

What is the purpose of the experiment?

Answer 25

is to quantify the number of males and hermaphrodites at different densities and provide a better understanding of fern reproduction and illustrate the impact of population density on sexual expression

Question 26

Why did we calculate the plate density rather than simply comparing the percentage of gametophyte sexual type of plates A-F?

Answer 26

because we want to know how many organisms there are. If we calculated the percentage, we would have to assume that every plate had the same number of spores, which is difficult to do because we don’t know how many spores there are and how to control the number amounts.

Question 27

What is the relationship between gametophyte density and sex expression?

Answer 27

as the density goes up, the percentage of males goes up slightly

Question 28

From an evolutionary perspective, why would such a relationship exist between gametophyte density and sex expression?

Answer 28

if we have more gametophytes, we have more ACe, and more males and fewer hermaphrodites

Question 29

what way is continuous data represented?

Answer 29

through a scatter plot graph (can take on any value within a range, including decimals)

Question 30

what way is discrete data represented?

Answer 30

through bar graphs (can only take on certain values, that doesn’t include decimals)