BIOLOGY 1

CHAPTER 21 , 22, 23 & 24

 

PLANTS:

10 Divisions of the Kingdom Plantae

           

Kingdom Plantae:

 

1.                  Evolved from green algae ( in ancient oceans and swamps)

2.                  Have evolved a variety of adaptations for obtaining water

and conserving water.

 

What is a Plant?

 

1.      Multicellular

2.      Eukaryote

3.      Cell wall of cellulose

4.      Waxy waterproof covering called a cuticle

5.      Capable of photosynthesis.

                                                                                                           

Evolution of Plants:

 

·                    500 million years ago – first plants appear, looked like moss.

·                    400 million years ago – first plant fossil, a psilophyte ( picture on p. 584 )

·                    All plants probably evolved from green algae.  Why?

                        Both algae and plants,

§         lived in ancient oceans

§         have cell wall of cellulose

§         have same types of chlorophyll

§         store food as a starch

 

Adaptations of Plants:

 

1.                  Preventing water loss

a.       Cuticle – waxy outer covering helps prevent water from evaporating;  most fruits, leaves and stems

 are covered with a cuticle.

b.       Stomata – openings (windows) in cuticle that allow CO2 and O2 to

be exchanged ( picture p. 586 )

           

2.                  Photosynthesis

a.       Leaf – broad flat organ of a plant –

(1)   responsible for trapping sunlight for photosynthesis

(2)   also gases are exchanged here

(3)   supported by stem, grows upward toward sunlight

(4)   have both upper and lower surfaces

 

3.                  Putting down Roots

a.       Soil – most plants depend on the soil as a primary source for water and other nutrients.

b.       Roots – a plant organ that;

(1)   absorbs water and minerals from the soil

(2)   transports nutrients to stems and leaves

(3)   anchors plant in the ground

(4)   starch (food) storage organ   (potato, radish)

                                                                                         

 

4.                  Transporting materials

a.       Stem – an organ of a plant that provides structural support and transportation of food and water

from roots to leaves and back.  Can also be a food storage site. (cellery, rhubarb)

 

b.       Vascular plants – contain stems that are tubelike structures

for transporting foods, water and nutrients.  (Most plants are vascular: pine tree, sunflower, ivy)

 

c.       Nonvascular plants – stems do not have vascular tissues.

Cells are few and nutrients travel by osmosis and diffusion

(moss).

 

Vascular plant tissue was important in evolution of plants that can live farther away from water, and are

stronger so they can grow larger.

 

5.                  Reproduction

 

a.       Seed – contains embryo and its food supply, covered by a protective coating.

b.       Spore – gamete and hard protective coating (moss, ferns)

c.       Pollen - sperm

 

6.                  Alternation of Generation

Two stages of generations:

a.       Gametophyte generation – responsible for development of

gametes;  male sperm, female egg  (1n)

b.       Sporophyte generation – responsible for production of spores  (2n) – “parent” stage

 

 

                                    Phylogeny of Plants:

 

Ten (10) Divisions of Plants

                                                Two (2) categories of divisions

non – seed plants

                                                        seed producing plants

 

A.        Non – Seed Plants:    (5 divisions)

 

            1.  Division Bryophyta – (mosses, Liverworts)

                        -  non vascular

                        -  small, prefer moist environments

                        -  gametophyte life stage dominant

                        -  sexual reproduction parts

·        protonema – filaments that are either male or female

·        antheridium – male reproductive parts; produce sperm ( pollen )

·        archegonium – female reproductive parts; produce egg ( seed )

- asexual reproduction

·        vegetative reproduction – pieces break off and generate a whole new plant

 

            2.  Division Psilophyta – (whisk ferns)

                        -  land dwellers

                        -  stem covered with leaf like scales

                        -  most found in tropics, but one species found in Southern

                           United States.

 

            3.  Division Lycophyta – (club mosses, spike mosses – not actually moss)

-         vascular plants

-         modern plants are small, but in dinosaur times they were huge

-         most ancient forests of these plants are now coal

-         strobilus – special leaves that protect reproductive cells; grow in spirals or whorls

-         prothallus – a germinated spore which will produce either male or female reproductive parts

                       

 

Vascular tissues – transport materials from one part of a plant to another.

            Two types:

            a.         Xylem – tissues of dead tube like cells that transport water

                        and minerals up from roots to leaves

            b.         Phloem – live tube like cells that transport sugars from

                        leaves down to the rest of the plant

 

 

            4.  Division Pherophyta – (ferns)

                        -  most well known group

                        -  wide variety of environments

                        -  most diverse seedless group

                        -  fronds – fern leaves

                        -  pinnae – leaflets of divided fronds

                        -  sorus/sori – clusters of spores usually found on the

                            underside of the pinnae

 

                        (insert drawing of a fern frond)

 

 

 

            5.  Division Sphenophyta – (horse tails, cat tails, reeds)

                        -  ancient vascular plants

                        -  rough in texture

                        -  hollow stems

-  most are fossils, only 15 species found today

 

 

Gymnosperms – general name used for vascular seed producing plants

-         seeds usually produced on cones

-         seeds not protected by a fruit, therefore they are“naked seeds”

 

                        Four ( 4 ) types of Gymnosperms

                                    1.  Cycadophyta

                                    2.  Ginkgophyta

                                    3.  Gnetophyta

                                    4.  Coniferophyta

 

Gymnosperms reproductive structures:

 

                        a.  Microspores – produced in the male cone; becomes pollen grains

                        b.  Megaspores – produced in female cone; becomes egg.

                        c.  Embryo – an organism at an early stage of growth and development

                        d.  Cotyledons – food storage organs of a plant embryo  (similar to chicken yolk)

                        e.  Pollen grain – a structure which allows the sperm to develop inside; it has nutrients and a

protective covering

f.        Ovule – a structure where the female gamete (“egg”) develops; wind carries

pollen grains to the ovule where polination (fertilization) happens forming an embryo.

Some embryos are enclosed within a protective structure; the seed.

 

Five Seed Producing Divisions:

 

            1.         Division Cycadophyta – (short palm-like trees)

                        -  exclusively in tropics, Florida is the only state in U.S. to have any of these plants

- male and female cones are housed on separate trees

 

2.         Division Gnetophyta – found only in Central and South

            America;  3 distinct types (genera)

            a.  Gnetum – tropica (climbing plants and vines)

            b.  Ephedra – shrub like plants;  may be found in U.S.

            c.  Welwitschia – found only in South Africa;  can be 100 years old; has only 2 leaves

 

3.         Division Ginkgophyta – (ginkgo biloba)

-   only 1 species left, the Ginkgo Biloba tree, it is a sacred tree of China and Japan

-         popular health food supplement

-         hardy plants, resistant to insects and air pollution

-         male trees often found inside shopping malls.  The female trees possess a fruit that

§         has the distinct odor of  rotting flesh so they are not often found inside.

-         Their polinators are flies.

 

 

            4.         Division Coniferophyta – (conifers)

                        -   largest most diverse group of gymnosperms

                        -   cone bearing trees like cedar, fir, pine, cypress,

                             redwood, and juniper

-         the oldest living trees in the world

-         leaves are modified into scales or needles

-         adapted to cold climates

 

Two types of Conifers:

a.         Evergreens –

-  keep leaves (needles) all year

-  needles may be kept 2 – 40 years before falling off

-  needles and branches are flexible which allows the

                            snow to slide off instead of breaking branches

-  most conifers are evergreen

           

                                                b.         Deciduous –

                                                            -  lose all leaves at the same time, usually in the fall of

                                                                the year

                                                            -  becomes dormant in winter

 

 

            How did Conifers get their name?

 

                        -   from their cones;  2 types of cones

 

a.        Male cones - are usually smaller and house pollen grains, found

most commonly on the bottom branches, they drop off as soon as pollen is released

b.       Female cones - are larger, they house the seeds, are commonly found

on the branches at the tops of the trees and may be kept up to 2 years to let seeds mature

 

            If both female and male cones are found on the same tree, the male

            cones are on the lower branches, the female cones in the tops of the

            trees.  This promotes cross fertilization by the wind.

 

 

5.       Division Anthophyta – (flowering plants)

 

-         not a gymnosperm because it produces fruit

-         generally known as Angiosperms; plants that produce flowers and develop seeds protected in a fruit

-         most well known plants on earth, found all over the world

-         have;   roots, stem, leaves, seeds, flowers, fruit

                        -     largest most diverse group of all seed plants

                        -     fossil records to 130 million years ago

-         seeds surrounded by fruit

-         roots and stems store food during environmentally unfriendly times (winter, drought, no sunlight)

§         food storage organs

·        bulbs – short stem with fleshy leaf base

·        corm -  short thick underground stem

·        tuber – swollen root or stem with buds that sprout new plants

 

 

            Two ( 2 ) Classes of Anthophyta:

 

                        a.  Monocotyledons – seeds having one cotyledon;  (grasses, orchids)

b…Dicotyledons – seeds have 2 cotyledons; (herbs and flowers)

 

( Remember that a cotyledon is a food storage area to nourish seeds)

 

           

 

Life Span of Anthophytes/Angiosperms

 

(their life span reflects its strategy for survival)

a. Annual-plants that only live for 1 year

-they sprout from seeds, grow, reproduce and die in 1 growing season

-most are herbaceous - stems are green and not woody (food plants-corn, wheat, peas, beans, watermelon).

 

                                    b. Biennials-plants that have a life span for 2 years

                                                -usually flower and seed once a year(carrots, beets, turnips)

                                         

c. Perennials-plants that can live for many years

-usually flower and seed once a year(grasses, deciduous trees)

 

 

Structures and their functions

 

                                     a. Roots-underground parts of a plant

                                                            - anchor plant

         - absorb water and minerals from soil

                                                            -some plants store food in the roots (carrots, potato)

 

 

                                                -Parts of a root

                                                            1.) epidermis - outer layer of cells

                                                            2.) root hair - hair-like extensions of roots

                                                            3.) cortex - transports water to vascular core,

·        Parenchyma-cells that make up the cortex, they sometimes store food and water.

4.) endodermis - innermost layer of cells, forms waterproof seal around the vascular tissue, controls the flow of water

5.) pericycle - tissue that gives rise to lateral roots

6.) cambium - tissue that produces xylem and phloem tissues

7.) root cap - protects the root tip where new root

cells are made; very tough protective layer

8.) apical meristem - dividing cells of the root tip

                                   

 

                                   b.  Stems-the above ground part of the plant

                                         - they support leaves and flowers

                                         -wide variety available

                                         -may be soft and flexible or hard and woody

 

                                                            Functions of Stem

·        support for all above ground parts

·        house vascular tissues for transport

 

                                                            Woody Stems

1.      can survive for many years

2.      stems grow thicker each year

3.      secondary growth-the added thickness, results in growth rings, can be  used to tell the age of plants

4.      Bark- tough, corky outer layer, protects plants from insects and herbivores

 

 

                                 c.   Leaves

1. traps sunlight for photosynthesis

            (often flat so they can absorb more sunlight)

2. petiole-the stalk that joins the leaf to the stem

3. veins- extend from petiole through leaf

4. transpiration-the evaporation of water from leaf’s

            stomata

                  5. guard cells-help reduce water loss by controlling the

            size of the stomata opening.

6. mesophyll-the photosynthetic tissue of a leaf, found just            

            beneath the epidermis

7.modified leaves- can be used for other functions (cactus          

            spines) 

 

 

4        leaf modifications

                                                a. thorns – rose bush, protection 

                           b. scales – cedar tree, prevents water loss and cold weather

                                         modification

                           c. needles – pine tree, prevents water loss and cold weather

                                         modification

                                                d. spines – cacti, protection

 

 

 

Reproductive Structures of a Flower 

 

  1. petals – leaf-like, found at the end of stem, arranged in a circle or corolla
  2. sepals – leaf-like, encircle petals
  3. stamen – inside petals, the male reproductive structure
  4. anther – on the tip of stamen, produces pollen
  5. pistil – inside flower on tip of stem, female reproductive structure
  6. ovary – enlarged bottom part of pistil – houses eggs

 

 

Complete flower has all 4 reproductive organs

(a)    petals

(b)    sepals

(c)    stamen

(d)   pistil  (both male and female parts), (morning glory, tiger lilly)

 

Incomplete flower – lacks one or more of the 4 reproductive organs

         - separate male and female flowers – (squash, corn)

 

Pollination – the process of transferring pollen grains from the anther to the stigma

 

            Ways pollination can occur:

·        wind – completely random

·        animal pollinators – bees, beetles, birs, bats, moths, butterflies – most flowers produce nectar which is a rich food source for animals

 

Ways to attract animals :

·        nectar – as the animal feed is brushes against the pollen which sticks to the animal and is taken to another flower when the animal moves

·        color – brightly colored petals help attract the proper animals; (butterflies like very vivid colors, moths feed at night so their plants tend to be pale in color, bees prefer bright yellow or blue)

·        scent – sweet or putrid smells depending on type of animal needed to pollinate; (flies – plants smell like rotting meat; bees – like very sweet smells)

Two types of pollination:

 

  1. self- pollination – the pollen  of a plant lands on its own pistil; offspring are

genetically similar to parent plant

  1. cross- pollintation – the pollen of one plant lands on the pistil of another plant;

most plants favor cross-pollination

 

Two adaptions to ensure cross-pollination

 

    1. anthers found high above flower so wind will blow pollen to other flowers

 

    1. anthers and pistils do not always mature (ripen) at the same time

 

 

Photoperiodism – a flowering plant’s response to length of days and nights

 

1.      short-day plants – (strawberries), poinsettias, cockleburs, ragweed);

bloom when days are shorter than nights           

2.      long-day plants – (peppermint, potato, peas, clover,carnations) –

bloom when days are longer than nights

3.      day- neutral plants – (most other plants)

– blooming controlled by temperature and moisture

   (other things beside day length)

 

 

Endosperm – the food storage tissue that supports development of plant embryo

 

Fruit – the enlarged ovary; it contains the seeds; aids in seed dispersal

 

 

2 Types of fruits

 

1.      fleshy – apples, grapes, melons, tomatoes, cucumbers

2.      dry – peanuts, walnuts, grains

 

Dormancy – when the seed is inactive, not growing or developing

·        this helps seeds survive harsh conditions that would kill a developing plant

·        can last for months or years (some weed seeds can survive for 100 years) – evening primrose, curly dock

 

Germination – the beginning of development of the seed into a plant

 

 

Tropism – a plants response to a favorable environmental stimulus (plants grow toward 

                   sunlight)

 

Nastic movement – a plant response not dependent on direction of stimulus; does not involve growth (venus fly trap closing)

 

Hormone – a chemical the plant makes that causes physiological change; only small amounts are needed (auxin – a growth hormone; helps plants grow and develop)