BIOL 191A Exam 2

streptophytes

plants and their closest green algal relatives

Name the terrestrial adaptations that land plants had to undergo.

1. bodies of **tissues**
2. formation of **apical meristems**
3. **alternation of generations**
4. embryos = multicellular sporophytes
5. spores for dry air dispersal
6. structures of gametangia, sporangia

tissues

association of many cells of the same type which prevents desiccation in plants

alternation of generations

life cycle alternates between multicellular diploid organisms, called sporophytes, and multicellular haploid organisms, gametophytes

apical meristems

groups of actively dividing cells at growing tips(shoot and root) which allow the production of thick, robust bodies in plants

Explain alternation of generations.

1. The multicellular diploid sporophyte undergoes meiosis to produce haploid spores.
2. The spores undergo mitosis which produces the haploid multicellular gametophyte.
3. Due to cell differentiation, the gametophyte differentiates into the gametes, the egg cell and the sperm cell.
4. These gametes unite during fertilization to form a diploid zygote.
5. The zygote undergoes mitosis which produces the diploid multicellular sporophyte.

Classify the 9 phyla of land plants.

^^Bryophytes(non-tracheophytes)^^

* ^^liverworts - earliest land plants^^
* ^^mosses^^
* ^^hornworts^^

(small, moist habitat, gametophyte dominant)

==seedless tracheophytes - conduction system(vascular system) and structural support from tracheids; stems, roots, and leaves==

\*\*maintain stable internal water content by vascular system, waxy cuticle, and stomata

* ==lycophytes - earliest vascular land plants==
* ==pteridophytes - modern ferns==

development of pollen and seeds

* gymnosperms - naked seeds
* Cycads
* Ginkgos
* conifers
* Gnetales
* Gnetum - broad leaves
* Ephedra - adaptations to conserve H2O
* Welwitschia - looks like seaweed in a desert
* %%angiosperms-- enclosed seeds via fruit%%
* flowers
* fruit
* endosperm

During plant evolution, the __________generation has become larger and more complex.

sporophyte

embryos

young, multicellular sporophytes

flower

a reproductive shoot; a short stem that produces reproductive organs instead of leaves

fruits

structures that develop from flowers, enclose seeds, and foster seed dispersal in the environment; develop from ovary walls that aid in the dispersal of the enclosed seeds

* helps with competition with larger parents
* attracts animals to eat them for seed dispersal

endosperm

nutritive tissue that increases the efficiency with which food is stored and used in the seeds of flowering plants

vascular system parts

1. xylem - conducts water and minerals throughout the plant body and provides structural support


1. lignin
2. tracheids
2. phloem - watery sap containing organic molecules such as sugar

tracheids

specialized conducting cell found in xylem, conducts water and structural support

ovule

in a seed plant, a megaspore-producing megasporangium and enclosing tissues known as integuments

wood

gymnosperms appear to have originated from ancestral plants that had the capacity to produce…, a tough material composed of xylem tissue

traits that angiosperms inherited from gymnosperms

1. capacity to produce wood
2. capacity to produce seeds

cycads

earliest-diverging modern gymnosperm phylum; spreading palm-like leaves and conelike structure; attracts beetles for pollinators

Ginkgo

Ginkgo biloba; tolerate heat, cold, and pollution better than many other trees, can live for more than 1,000 years

conifers

named for seed cones, more than 50 genera; produce simple pollen cones and more complex, ovule-bearing cones; includes the Gnetales

evolutionary success of angiosperms traits

1. flowers - foster seed production
2. fruits - favor seed dispersal
3. endosperm - food helps embryos within seeds grow into seedlings

four types of flower organs

1. sepals
2. petals
3. pollen-producing stamens
4. ovule-producing carpels

petal

attracts insects or other animals for pollen transport

sepals

forms outer layer of flower buds; protect the unopened flower bud

perianth

all of flower’s sepals and petals

stamens

structures that produce and disperse pollen; consists of the anther and filaments; produce ale gametophytes and foster their early development

filament

elongate stalk in stamens, contains vascular tissue that devlivers nutrients to the anthers

anther

a group of four sporangia that produces spores; many diploid cells undergo meiosis within the sporangia, producing tiny haploid microspores

carpel

flower shoot organ that produces ovules that contain female gametophytes; vase-shaped structures that produce, enclose, and nurture female gametophytes; contain veins of vascular tissue that deliver nutrients to the developing gametophytes

pistil

consists of carpels, fused carpels, and contains the stigma, style, and ovary; single carpel or several fused carpet,s

stigma

allows pollen to germinate; produces long pollen tube that grows through the style; receives pollen grains

ovary

lowermost portion of the pistil that encloses and protects the ovules

double fertilization

process in angiosperms where one sperm fuses with the egg nucleus to form a zygote, and the other sperm nucleus fuses with the nuclei of other haploid cells of the female gametophyte(central cell)→development of endosperm

→ fed by the endosperm, the zygote develops into an embryo, and the ovule develops into a seed

→ ovaries develop into fruits

monocots

one of the two largest lineages of flowering plants in which the embryo produces a single seed leaf(cotyledon), magnoliids related

eudicots

one of the two largest lineages of flowering plants in which the embryo possesses two seed leaves(cotyledons), magnoliids related

cotyledons

embryonic leaves; eudicot embryos will become heart shaped once these begin to develop

Name the methods for effective pollination due to flower evolution.

1. fused petals that form foral tubes; accumulate nectar and attract pollinators
2. inflorescences - greater surface area of pollination in shorter amount of time, flowers clustered together
3. grasses feature flowers with few/no perianths which fosters pollination by wind

secondary metabolites

all plants produce these; organic compounds that are not essential for basic cell structure and growth but aid in survival, structure, and reproduction(like a steroid boost to make you more physically fit)

2 major classes in plants of secondary metabolites

1. **terpenes and terpenoids** - ex. citronella, rubber, turpentine, amber
2. **phenolics** - responsible for some colors and the distinctive flavors of cinnamon, nutmeg, ginger, cloves, chilies, vanilla; some antioxidants; some absorb UV radiation
3. **alkaloids** - affect animal nervous system; ex. caffeine, nicotine, morphine, ephedrine, cocaine, and codeine

domestication

process of artificial selection, where traits that are desirable to humans are selected

Name some ways humans have domesticated plants.

* larger grains, greater numbers of grains, softer grains
* loss of shattering - ears of wild grains break apart and shatter their grains
* domesticated number of plants for vegetables

_____________and_____________ form the transitions between the sporophyte and gametophyte life stages, and link them in a cycle.

Meiosis; fertilization

stamens and carpels

produce distinctive types of spores by the process of meiosis → tiny multicellular gametophytes develop from these spores

pollen grains

develop from microspores; immature male gametophytes; dispersed through pores or slits in the anthers; develop within sporangia located in the anthers of stamens

pollen tube

during a later phase of development; mature male gametophyte produces sperm cells, the male gametes

ovule

consists of a spore-producing sporangium and enclosing tissues known as integument

Explain what happens within an ovule

1. a diploid cell produces four haploid megaspores by meiosis
2. within each group of four megaspores, three die, which allows the surviving one to gain more nutrients; this surviving megaspore generates a female gametophyte by mitosis
3. female gametophyte typically consists of 7 cells, one of which is the female gamete, the egg cell

pollination

occurs prior to fertilization; involves released pollen grains finding their way to the stigma of a compatible flower

self-pollination

occurs when pollen from the anthers of a flower is transferred to the stigma of the same flower or between flowers of the same plant

cross-pollination

occurs when a stigma receives pollen from a different plant of the same species

Fertilization doesn’t only unite the gametes to a zygote to develop into an embryo, but also…

triggers the transformation of ovules into seeds and ovaries into fruits; embryo, seed, and fruit development happen at the same time

triploid endosperm

the result of a sperm fusing with the two nuclei in the central cell of the female gametophyte, will be the nutritive tissue for the developing embryo

each seed contains…

an embryo and nutritive endosperm tissue, enclosed and protected by a seed coat(develops from ovule integuments); when fully matured, they undergo drying and enter a phase of dormancy

seed germination

the process in which an embryo abosrbs water, become metabolically active, and grows out of the seed coat, producing a seedling(if seedling obtains sufficient nutrients, will grow into mature sporophyte)

flowering time

controlled by the integration of environmental information such as temperature and day length(photoperiod) with hormonal influences and circadian rhythms\*\*biological and physical stimuli

* FT mobile protein to signal shoot meristems to produce flowers

vernalization

process by which cold exposure allows plants to flower in spring

organ identity genes

specify the four basic flower organs: sepals, petals, stamens, and carpels(other genes determine other flower aspects)

whorls

four concentric rings which sepals, petals, stamens, and carpels occur in

* perianth consists of the calyx plus the corolla

calyx

sepals are collectively known as(whorls)

corolla

petals are collectively known as(whorls)

androecium

stamens are collectively known as the(whorls)

gynoecium

carpels are collectively known as(whorls)

complete flowers

a flower that possesses all four types of flower organs

incomplete flower

a flower that lacks one or more of the four flower organ types

perfect flowers

flowers that have both stamens and carpels

imperfect flowers

flowers lacking stamens or carpels

* carpellate flower - produces only carpels
* pistillate flower - produces only pistils

variation in flower organ number

* eudicot flower organs often occur in 4s or 5s or their multiples
* monocot flower organs often occur in 3s or multiples of 3

variation in flower color

* sepals tend to be green, petals tend ot be colorful and fragrant

variation in flower fragrance

* fragrances result from secondary metabolites that diffuse into the air
* genetic variation in the synthesis of different types of secondary metabolites is responsible for the many types of flower scents

flower shape variation resulting from organ fusion

many flowers undergo genetically controlled fusion between whorls or fusion of the organs within a whorl

* ex. some flowers have petals that are fused together to form a tube, which holds nectar consumed by animal pollinators

variations in flower symmetry

* flowers may have radial or bilateral symmetry
* under genetic control
* CYCLOIDEA gene → bilateral symmetry

sporangia

where pollen grains develop; located in the anthers of stamens; microspores develop into pollen grains

The development of **microspores** into pollen grains involves…

1. microspore division to produce the youngest type of male gametophyte
2. development of a tough, protective pollen wall

Explain the development of pollen grains within the sporangia.

1. diploid cells that are located inside protective sporangia undergo meiosis to produce a cluster of four haploid microspores, each with a thin cellulose cell wall
2. microspore division to produce the youngest type of male gametophye


1. each microspore nucleus undergoes one or two mitotic divisions to form an immature male gametophyte


1. first division gives rise to a tube cell and a generative cell suspended within the tube cell

generative cell

in a seed plant, one of the cells resulting from the division of a microspore; a generative cell divides to produce 2 sperm cells either before or after pollination

tube cell

produces the pollen tube, which delivers sperm to the female gametophyte

The __________and the__ ___________determine whether or not pollen grains germinate and pollen tubes grow toward ovules

stigma; style

self-compatible plants

can self-pollinate

self-incompatible(SI) plants

prevent the germination of pollen that is too genetically similar to the pistil

* recognition involves interaction between proteins of pollen and pistil cells(and influences the ability of pollen to rehydrate)

each ovule produces…

a single female gametophyte, which consists of 7 cells and 8 nuclei

central cell

in addition to the egg cell, involved in double fertilization; in the female gametophyte of a flowering plant, a large cell that contains two nuceli; after double fertilization, it forms the first cell of the nutritive endosperm tissue

Explain what happens when pollen grains germinate successfully.

They take up water and the tube cell produces a long pollen tube.


1. Within the tube, the generative cell divides by mitosis to produce two sperm cells(tube must grow at tip from stigma, through style, to the ovule) → this is controlled by tube cell nucleus
2. during tip growth, new cytoplasm and wall materials are added to the tip of an elongating cell
3. when pollen tube encounters the opening(micropyle of an ovule), tip wall bursts, releasing the sperm ;D

Why do the embryo and endosperm from double fertilization have different fates despite similar genetic composition from the generative cell?

Plant endosperm undergoes genomic imprinting by DNA methylation; imprinting causes gene expression to occur differently in plant endosperm than it does in the embryo

embryogenesis

the process by which embryos develop from single-celled zygotes by mitotic divisions fueled by endosperm nutrients

What are major components of angiosperm reproduction and are essential to animal nutrition?

1. seeds - contain dormant plant embryos that may develop into seedlings under favorable conditions
2. fruits - aid seed dispersal, which allows plants to colonize new sites

Since embryos, seeds, and fruits mature AT THE SAME TIME what is their development coordinated by?

hormonal signals

established apical-basal polarity

first unequal mitotic divisions of embryogenesis(process that creates embryo); smaller cell will become the embryo, the larger cell, the suspensor

Explain the process of embryogenesis

1. zygote divides unequally; smaller cell will become embryo; larger cell, the suspensor
2. young embryo begins to develop as a sphere with nutrients provided by the suspensor and parent plant
3. cotyledons and root and shoot meristems start to develop, forming the heart stage
4. embryo develop supported by surrounding endosperm tissue
5. mature embryo has absorbed most of endosperm nutrients, filling the seed; protective seed coat develops from ovule integuments

apical basal polarity

the result of the first unequal division in embryogenesis; establishes young shoot and root at apical and basal poles with auxin and mobile protein transcription factor; SAM occurs at the apical pole, RAM occurs at the basal pole

epicotyl

the portion of an embryonic plant stem with two tiny leaves in a first bud; located above the point of attachment of the cotyledons

What is the difference between mature eudicot embryos and mature monocot embryos?

mature eudicot embryos(beans and peas) - displays an epicotyl and hypocotyl; radicle, embryonic root, extends from the hypocotyl; a lot of endosperm has been absorbed into large cotyledons

mature monocot embryos(corn) - epicotyl with a first bud enclosed in the coleoptile; young monocot root enclosed within protective envelope known as the coleorhiza; contain large quantity of endosperm which is the huge vacuole looking thing in the diagram

As you can see, plants vary in which the embryonic shoot emerges, different roots and shoot and stuff.

hypocotyl(eudicot seeds)

portion of the embryonic stem located below the point of attachment of the cotyledons

radicle(eudicot seeds)

embryonic root which extends from the hypocotyl

coleoptile(monocot seeds)

protective sheath which encloses an epicotyl within a first bud

coleorhiza(monocot seed)

protective envelope which encloses the young monocot root

What may happen as fruits mature? They develop from ovaries.

* outer cuticle becomes very thick to prevent microbe attack
* mature fruits inc. sugar and acid content which produces distinctive tastes
* produce fragrant volatile compounds

asexual reproductive structures and mechanisms(3)

roots, stems, and leaves

* production of plant clones from non-reproductive plant organs
* somatic embryogenesis
* apomixis

somatic embryos

can develop from many types of plant somatic cells; do not produce root and shoot systems; do not have endosperm and do not develop within a seed; embryogenesis occurs naturally in some plants and used for cloning in asexual reproduction

apomixis

natural asexual reproductive process in which fruits and seeds are produced in the absence of fertilization

What is the difference between somatic embryogensis and apomixis?

somatic embryogensis doesn’t involve fruit and seed production