practical lab 2: kingdom plantae

what group of organisms did terrestial plants descend from?

Green algae called the Charophytes

what do aquatic green algae and land plants must do in order to survive and reproduce?

1. they must be able to absorb light for photosynthesis

2. They will need to absorb water from their surroundings and make sure it is available to all the cells of the organism

3. they will need a supply of carbon dioxide and nitrogen compounds that are needed to build the cell's organic molecules

reproduction in algae compared to terrestial

Terrestial reproduction cycles have more things to consider than those in water

• such as the protection of the delicare gamete forming structures, problems of gamete transfer, and survival of delicare young during reproduction

Algae in wet, stable aquatic environments don't need to keep these into consideration such as protectin their reproductive structures

alternation of generations

where plants spend a part of their life cycle as multicellular haploid gametophytes and part of their life vycle as multicellular diploid sporophytes

• they alternate!

5 features common in every plant life cycle (1-3)

1. Sexual reproducrion always includes the proccesses of meiosis and fertilization

2. Asexual reproduction never includes either

3. sexual reproduction always has a portion of the cycle in which all cells of the organism are haploid (gametophyte generation), alternating with a portion of the cycle in which all cells of the organism are diploid (sporophyte generation). This is the concept of alternation of generations

5 features common in every plant life cycle #4 - sporangia + spores

Sporophyte portion always ends with the production of spors by meiosis (meiospores)

• They are produced in a struture called sporangium (sporangia)

5 features common in every plant life cycle #4 - gametes + gametangia

Gametophyte portion of the cycle begins with the production of gametes by mitosis

• They are produced in a structure called gametangium (gametangia)

5 features common in every plant life cycle #4 - two types of gametangia

• Egg producing gametangia - archegonia (archegonium)

• sperm producing gametangia - antheridia (antheridium)

5 features common in every plant life cycle (5)

5. Asexual reproduction always results in the formation of new individuals which are genetically identical to the parent organisms.

advantages and disadvantages to asexual reproduction

Only advantageous if the organism is well suited to it's environment and if that environment is stable.

• a big disadvantage is that most environments are less stable, meaning that little genetic variation from asexual reproduction can be detrimental

  • one problem or change can cause a whole mass of plants to die if they are genetically identical

advantages of sexual reproduction

Sexual reproduction can allow for some plants to withstand less stable environments

• the genetic variability makes certain plants more fit in certain environments

how has natural selection occur in plants?

Natural selection not only worked on the morphological characterics but also the structures and strategies involved in sexual reproduction.

Fitness definition

refers to the ability to produce the greatest number of offspring that live to reproduce themselves

• the more “fit” a species is, the more successful they will be in the environment

Survival of the gamete forming organs

When exposed to the dry air, the gametangia on the gametophyte need an outer layer of protective cells to prevent them from drying out

Getting the gametes together

Transfer of the male gametes from the antheridium where they are made, to the eggs inside the archegonia

• this is harder to do on land than it was in the water

Getting the gametes together - mosses and ferns

the sperm in both of these are flagellated, and require free water for the sperm to swim through.

• the availability of water (rain) can severly limit the transfer of gametes and ultimately the success of reproduction

Getting the gametes together - flowering plants

In flowering plants, natural selection has favoured the loss of motility of the sperm and a reduction in the size of the gametophytes.

• This means water is no longer needed in gamete transfer.

  • which allowed for them to successfully reproduce in much dryer habitats.

Protection of the delicate embryo

Making sure the the dividing zygot does not dry out

• this is done by having the embryo develop inside the female archegonia

  • the wall of the archegonia even grows along with the embryo making sure it stays covered until it is well developed to protect itself from the dry air

to be diploid or not to be? - mosses

The dominant generation in this life cycle is the haploid gametophyte

• meaning the most obvious, longest lived, easiest to find generation.

to be diploid or not to be? - ferns

the dominant generation becomes the diploid sporophyte

• the gametophyte is very small, delicate, and lives only long enough to produce gametes and get the diploid embryo started

to be diploid or not to be? - flowering plants

the male and female gametophytes have been reduced

• in the female gametophyte it is a 7 celled-8 nucleate female gametophyte

• in the male it is 2 nuclei in the male gametophyte

Phylum Bryophyta - mosses

These generally occupy habitats which are damp and shaded

• The habitats are considered to be transitional areas between the aquatic and terrestial environments

  • -only a few that exist in dry ares require readily available water for reproduction

Reproduction in phylum bryophyta, mosses

Gametophyte generation is dominant

• There are two phases in the generation

  • first to develop is an algal-like filamentous phase is termed protonema. This can grow into either an antheridia or archegonia

  • second phase is the mature gametophyte, which is green and leafy

    • there is also an embryo in the sporophyte phase, which is an undifferentiated mass of cells, nourished and protected within the archegonia by the gametophyte

Reproduction in Phylum Bryophyta - Protonema

spores released from the capsule on mature sporophytes grow into protonema

• the protonema doesn't do anything but grow

  • can grow into either male gametophyte with antheridia or female gametophyte with archegonia

Reproduction in Phylum Bryophyta - Male gametophyte

Male gametophytes have cups that are called the antheridia

• the antheridia creates sperm that will be carried by water to the female gametophyte

  • these are haploid

Reproduction in Phylum Bryophyta - Female gametophyte

Female gametophytes have no cup but contain the archegonia

• the archegonia contains an egg that is inside the archegonia walls

from the naked eye what sets apart female and male gametophytes?

males have yellow cups on the tips of the plant while females do not

Reproduction in Phylum Bryophyta - Fertilization + zygote

Sperm from the antheridia travel by water (rain drop) and into a tube in the archegonia to reach the egg to fertilize it

• this will create a zygote which will grow via mitosis into an embryo

  • which will grow into a sporophyte

Reproduction in Phylum Bryophyta - sporophyte

The sporophyte will grow out of the female gametophyte (archegonia) and will develop a foot, seta, and a capsule

• the capsule is where spores are produced via meiosis

  • the capsule will then release the spores which will grow into protonema

Sporophyte anatomy

Foot - the point where the sporophyte is attached to the archegonium/female gametophyte

Seta - the long stalk of the sporophyte

Capsule - contains spores

• has an operculum

Sporophyte anatomy - capsule

The capsule creates the spores that will be distributed to grow into protonema

• the capsule has a protective covering to keep the spores in until they are mature, is called the operculum

  • this will fall off after the spores are mature and allow them to leave the capsule carried off by the wind

Asexual reproduction in moss

This is done through the process of fragmentation

• where any part of the gametophyte plant is capable of regenerating the protonemal phase which will grow into a mature gamtophyte

  • the leaves, stems, and rhizoids will all produce new protonemata if the environment is favourable

Phylum Monilophyta - Ferns

Mostly found in areas of damp soil, high humiditym and low life

• The sporophyte generation is dominant while the gametophyte generation is small vulnerable transitory phase

  • they also contain the adaptation of true vascular tissue

Differences in sexual reproduction of ferns from mosses

1. Increase in number of meiospores

2. the independence of the mature stages of both generations

3. the dominance of the sporophyte generation

Similartities of sexual reproduction between ferns and mosses

1. Presence of flagellated sperm cells

2. the dependence on free water for fertilization

3. the formation of an embryo which is protected and nourished by the gametophyte plant

4. they need to establish the gametophyte generation from a single unprotected spore

Fern development - Prothallus

It has a heart shape to the structure

• contains male and female gametangia

Fern development - Male gametangia

Antheridia - located on the outer edge of the heart, these produces sperm

Fern Development - Female gametangia + fertilization

Archegonia - located near the notch of the heart, contains the egg

• The sperm from the antheridia will travel into the archegonia through a gap where it will meet with the egg and fertilization

Fern development - Young Sporophyte

After fertilization the embryo is located in the region of the rhizome. The young sporophyte will grow of the of the notch of the gametophyte.

Fern development - Mature sporophyte

This structure is large and long with leaves

• has sporangium called sori (sorus) which are brown and contain spores

Fern development - Sori

Sporangia that are brown capsules which contain meiospores.

• They also have stalk (which is the stem of the sporangia)

  • and an annulus which serves as a protective barrier

Flowering plants

These are the most successful plants

• they can be found in almost every terrestial habitat

Reproductive adaptation in flowering plants - #1

1. Sporophytes are still dominant in flowering plants

• while the gametophytes of flowering plants are even more reduced

Reproductive adaptation in flowering plants - gametophyte

• the female gametophyte and young embryos are protected from many environmental stresses

  • this is because they are retained within the moist sporangia of the parental sporophyte

Reproductive adaptation in flowering plants - #2

2. The seed is the resistant life cycle (comparable to spores)

• It differs from spores because it is multicellular and contains a sporophyte embryo packaged with a food supply within a protective coat

Reproductive adaptation in flowering plants - #3

3. how male gametes disperse themselves in harsh terrestial environment

• this is done by the pollen grain, which are really tough structures that can be dispersed by the wind or animals.

  • this solves the problem of needing water to disperse the sperm like in ferns or mosses

Asexual reproduction in flowering plants

A lot of seed plants use this form of reproduction

• They only use this form if the environment is stable for many generations

• variability may not be as essential to the survival of the species

• if the environment is harsh, and the delicate organs/stages of sexual reproduction may not be able to survive

• This is especially helpful when in new environments finding a mate for sexual reproduction may be difficult or impossible

  • Asexual reproduction is not as complex and requires less energy

types of asexual reproduction - Rhizomes

occurs in grasses, cattails, sedges

• They will produce underground stems or rhizomes

  • these will grow through the soil and produce adventitious roots and a new above ground shoot

    • if it dies a new plant will have been formed already

types of asexual reproduction - Tubers

These are modified rhizomes in plants like potatoes

• They develop when specialized stem branches grown down into the grown and swell up with starch containing cells

  • Buds on the tubers will grow into new plants

types of asexual reproduction - Runners (stolons)

These are horizontally growing stems that produce few or many leaves

• At a place where a leaf would normally develop, a node, it will produce adventitious roots down into the soil and new above ground shoots instead

types of asexual reproduction - Plantlets

occurs in duckweed (aquatic) and Kalanchoe sp.

• they will produce miniture plants on the margin of their leaves

  • these will fall off and evelop into mater plants

types of asexual reproduction - Bulbs

occurs in onions chives and lilies

• Over-winter in the form of a bulb

  • each bulb has a very short stem which is surrounded by fleshy leaves

    • in the spring, the shoot apex begins to grow using the nutrients stored in the leaves

types of asexual reproduction - Corms

These are similar to bulbs except that there are no storage leaves

• The nutrients are, instead, stored in the swollen stem

Sexual reproduction in Flowering plants - the reproductive organ

Known as the flower

• This is part of the sporophyte generation which functions to protect the developing gametes and to ensure pollination and fertilization

  • They are generally composed of the male and female reproductive structures

Sexual reproduction in Flowering plants - The perianth

These are attractive or protective leaf like structures that surround the male and female reproductive structures

Sexual reproduction in Flowering plants - Fertilization/pollination

Since they are rooted structures they have to use other transfer agents to complete fertilization

• This includes, wind, water, and biological agents

  • such as, insects, birds, and mammal transfer the pollen (male gametes) from plant to plant

Sexual reproduction in Flowering plants - sepals

these develop first and are usually green in colour

• found on the underside of petals

  • they provide protection for the delicate internal structurees and a small amount of food through photosynthesis

Sexual reproduction in Flowering plants - petals

these are te brightly coloured leaf-like structures

• they also provide protection and their arrangement is an attractant to the various animals such as insects who are necessary for transfer of gametes

Sexual reproduction in Flowering plants - Male reproductive structure (sporangia)

Called the stamen

• consists of the anther and filament

  • where the production of pollen grains occur

    • forms male gametes via mitosis

Sexual reproduction in Flowering plants - Development of the male gametophyte - Microsporangium

• inside of the anther, the microsporangium has cells called microsporocytes.

  • these undergo meiosis to produce microspores

Sexual reproduction in Flowering plants - Development of the male gametophyte - Microspores

• each microspore will divide mitotically once to produce two nuclei that will be encased in a thick wall, this forms the pollen grain

Sexual reproduction in Flowering plants - Development of the male gametophyte - Pollen grains + pollination

• the pollen grains will be released and transferred to the stigma of the flower (pollination)

  • the tube nucleus produces the pollen tube, which penetrates the stigma and grows through the style until it reaches the ovary

    • by this time, the nucleus has divided once to produce two sperm nuclei

      • this creates a 3-nucleated structure, aka the mature male gametophyte

Sexual reproduction in Flowering plants - carpel

the most central structure within the flower

• a leaf that is modified to produce ovules

  • consists of the:

  • stigma, the sticky surface designed to receive pollen grains

  • a style, the slender stalk where the pollen tube grows

  • an ovary, which contains the ovules

Sexual reproduction in Flowering plants - Development of the Female gametophyte - the ovule and megasporangium

contains the megasporangium

• the megasporangium produces one megasporocyte

Sexual reproduction in Flowering plants - Development of the Female gametophyte - the megasporocyte

this will undergo meiosis which will produce four haploid cells or megaspores

Sexual reproduction in Flowering plants - Development of the Female gametophyte - megaspores

three of the megaspores will disintergrate and the remaining one will divide mitotically three times

• this produces an 8-nucleate, 7-celled structure

  • this is the mature female gametophyte

    • there are synergid cells by the micropyle (an opening) (3 cells with 1 nuclei each)

    • one polar nuclei in the center (1 cell with 2 nuclei)

    • and antipodal cells by the top (3 cells with 1 nuclei each)

important aspects of gametophyte development in seed plants

1. no release of spores from the sporophyte

2. smalle size of gametophyte; pollen grains = small = easier to trasnfer; embryo sac = small = better protected

3. neither antehridia nor archegonia are produced

4. sperm nuclei, rather than sperm cells which eliminate the dependence on water

Pollination

occurs when pollen is trasnported to the surface of the flower's stigma

Pollination process - pollen and pollen tube

• the pollen is transported to the surface of the flower's stigma

  • then produces a tube that will grow down the style and into the ovary of the ovule

Pollination process - ovule + embryo sac

to reach the ovule, it is only capable of growing through the opening in the integument of the ovule to the embryo sac

• the pollen tube will fuse with the embryo sac membrane and release two sperm nuclei into the sac

Pollination process - double fertilization

• One sperm nucleus will fuse with the egg nucleus to form the zygote

• while the other sperm nucleus fuses with the two polar nuclei to form a triploid endosperm nucleus

Pollination process - triploid endosperm nucleus

This is capable of dividing quickly and governing the formation of food material to nourish the developing zygote

Pollination process - seed

where the ovule and the zygote are now termed seed after the triploid nucleus has divided

Seed development - seed

a mature ovule

• includes a seed coat, a food supply, and an embryo

Seed development - Integument

the integument will be converted into a resistant seed coat

Seed development - embryo + endosperm

the embryo grows and absorbs the endosperm

• it will store those nutrients in two “seed leaves" called cotyledons

Seed development - radicle

the basal portion of the embryo

this turns into the root system

Seed development - hypocotyl

the middle portion of the embryo

this turns into the connection between the roots and the stem

Seed development - epicotyl

the part attached to the cotyledons

this creates the stem, flowers, and the leaves

Fruit Development

Fruits will begin to develop after pollination and usually develop from the ovary

• but occasionally other parts of the flower are involved

Fruit Development - ovary

the cells of the ovary wall expand and the whole ovary enlarged to make room for the developing seeds

• the size and differentiation of the cells depend of the type of fruit

Fruit Development - large fleshy fruits

these develop water-resistant outer layer and secual inner layers of large water storage cells

• these fruits’ seed dispersal are by the means of animals

  • aka by eating, and pooping it out (seeds are not digested)

Fruit Development - dry fruits

these provide a covering that adhears tightly to the seed coat and will prevent drying out

• there are different kinds of dispersal for dry fruits

  • e.g. dandelions’ fruit act like a kite or balloon that enhance wind dispersal

    • other plants use animals to carry seeds by having the fruits to have burrs that will cling to animal fur or human clothing

      • while some are designed to open violently to disperse their seeds