Plant Biology Lab: Final Exam Notes

Genetics and Heredity

Definitions

DNA - polymer composed of repeating subunits called nucleotides

Nucleotides - adenine, thymine, cytosine, and guanine; 5-carbon sugars composed of a phosphate and a nitrogenous base

Purines - nucleotides with two rings (A and G)

Pyrimidines - nucleotides with one ring (T and C)

Locus - location of gene on a chromosome

Allele - variation of genes

Homozygous - two identical alleles at a locus

Heterozygous - two different alleles at a locus

Genotype - genetic makeup

Phenotype - physical appearance

Two principles of Mendelian genetics - principle of segregation and principle of independent assortment

Principle of segregation - two members of a gene pair separate during meiosis

Principle of independent assortment - the segregation of one allele pair is independent of the equal segregation of the other allele pair

Monohybrid and Dihybrid crosses

The results of crossing two heterozygous parents in a monohybrid cross are a phenotypic ration of 3:1 and a genotypic ratio of 1:2:1 assuming that there is no incomplete dominance at play

The results of crossing two heterozygous parents in a dihybrid cross is a genotypic ratio of 1:2:1:2:4:2:1:2:1 and a phenotypic ratio of 9:3:3:1

Quiz and Lab Sheet Answers

Alleles are different variations of genes

Adenine, thymine, guanine, and cytosine are the nucleotides present in DNA

The phenotypic ratio of a dihybrid cross is 9:3:3:1

DNA is located in the nucleus

DNA molecules are in the shape of a double helix

When extracting DNA, ethanol is ice cold to make the DNA condense

When extracting DNA extraction buffers are used to break down membranes

Bryophytes and Ferns

Introduction

Bryophytes are non-vascular plants

Ferns are seedless vascular plants

Alteration of generations refers to the two phases that occur in cycles in plants that undergo sexual reproduction. The two primary stages are gametophyte and sporophyte

In more primitive plants, such as mosses, the gametophyte stage is dominant.

Higher plants like ferns and fern allies have sporophyte stage as dominant.

Gametophytes produce gametes in a social structure called a gametangium

Sporophytes produce spores in a structure called a sporangium

Bryophytes

Bryophytes include mosses, liverworts, and hornworts. We are Most familiar with mosses most of the time.

In bryophytes the sporophytes are dependent on the gametophytes

Sexual reproduction requires water in bryophytes

Sex Organs in Bryophytes

The male sex organ of a moss is the antheridium

The female sex organ is the archegonium

Protonema - one of the earliest stages in a moss’s life cycle. When a moss spore geminates it results in a mass of thread-like or flattened tissues

Calyptra - covering tissue for a capsule containing spores

Operculum - bud cap that covers the peristome

Peristome - modified opening consisting of a ring of “teeth” that allows for gradual release of spores

Seedless Vascular Plants

Ferns!

Classified as vascular because they have xylem and phloem. Also differentiated from bryophytes due to the presence of roots, stems, and leaves.

Dominant phase is sporophyte

Sexual reproduction requires water

Frond - diploid sporophyte

Sorus - collection of sporangia where meiosis occurs

Each dot in an individual sorus, a cluster of sporangia

Indium - a papery covering over the sorus that protects the sporangia from excessive air exposure, drying, and other hazards

The gametophyte stage in the life of a fern is known as the prothallus

Quiz and Sheet Answers

What is the dominant phase of bryophytes? Gametophyte

What is the dominant phase of ferns? Sporophyte

What is the male sex organ of moss? Antheridium

What is the female sex organ of moss? Archegonium

Sheet is only the life cycles! Be sure to review them.

Kingdoms Bacteria, Protista, and Fungi

Taxonomy and Classification

Three domains (Bacteria, Archaea, and Eukarya) split into six kingdoms (Bacteria, Archaea, Protista, Fungi, Plantae, and Animalia)

Protists are eukaryotes that are never multicellular and do not show differentiation into tissues

These are followed by phylum, class, order, family, genus, and species

Eukaryotic cells have nuclei and membrane-bound organelles

Prokaryotic cells lack nuclei and membrane-bound organelles

Autotrophic - synthesizes its own food

Heterotrophic - feed on others

Domain Bacteria Kingdom Bacteria

Includes prokaryotic cells that undergo reproduction asexually via fission.

Heterocyst - special nitrogen fixing cells; often a large, transparent, thick-walled cell found in the filaments of certain blue-green algae and in certain fungi

Domain Eukarya Kingdom Protista

Contains eukaryotic cells that are mostly autotrophic

Reproduce sexually and asexually

Includes Spirogyra which has spiral chloroplasts

Pyrenoids - protein body in algal chloroplasts involved in carbon fixation, starch formation, and starch storage

Euglena can detect light

Diatoms!

Kingdom Fungi

Fungi are grouped by the type of sexual spores they produce into three phylum: Zygomycota, Ascomycota, and Basidiomycota

Fungi are eukaryotic and reproduce using spores. They are differentiated from plants due to their heterotrophic nature and their cell walls being made up of chitin rather than cellulose.

Spores are units of asexual reproduction. A single spore developed into a new organism

Gametes are units of sexual reproduction. Two gametes need to fuse to create a new organism

Zygomycota

Sexual spores are thick-walled spores called zygospores

Spores occur in the sporangium in Zygomycota

Filaments are called hyphae, a mass of hyphae is called mycelium

Mycelium is the vegetative part of a fungus consisting of a mass of branching, thread-like hyphae.

Rhizopus - a genus of fungi within the Zygomycetes class, example is the fungus that grows on bread.

Columella - a sterile structure that extends into and supports the sporangium. May actually belong to the host organism instead of the fungi itself

Sporangiophore - a specialized hypha bearing sporangia

When a plus strain of bread mold meets a minus strain, the two hyphae create structures called gametangia, fusing and exchanging chromosomes in a process called karyogamy

Zygospores are held in place by suspensor cells made up of the former gametangia. They have thick coats known as zygosporangium to prevent drying out or destruction from ultraviolet rays

Karyogamy only occurs when conditions are unfavorable for the other kind of growth. Otherwise, bread mold typically propagated via asexual reproduction.

Ascomycota

Ascomycota - spores internally borne in a sac called an ascus

Example include morels and truffles

Spores occur in the conidia in ascomycota.

Plasmogamy - the cytoplasm of two parent cells fuses together without the fusion of nuclei, effectively bringing two haploid nuclei close together in the same cell

Basidiomycota

In Basidiomycota spores are borne externally on a club shaped structure known as a basidium

Sterigmata - a spore-bearing projection from a cell

Overview

How can you separate the three major lineages of fungi?

In Zygomycota sexual spores are thick-walled, resting spores called zygospores

In Ascomycota spores are borne internally in a sac called an ascus

In Basidiomycota spores are borne externally on a club-shaped structure called a basidium

Gymnosperms and Angiosperms

Gymnosperms are cone-bearing plants

Angiosperms are flowering plants

Homosporous plants have one spore type. They tend to be haploid and develop into gametophytes in mosses and ferns

Heterosporous have two spore types, the megaspore and microspore, on the same plant

Megaspore is a female spore that develops into a female gametophyte (example: the cones on evergreen trees)

Microspore is a male spore that develops in a male gametophyte. They are smaller and grow in clusters at the tips of branches.

Gymnosperms

Main characteristics:

• In gymnosperms seeds are not enclosed in an ovary that develops into a fruit
• Gymnosperms have a vascular system
• Gymnosperms are heterosporous
• Gymnosperms are sporophyte dominant
• Water is not required for reproduction in gymnosperms
• In gymnosperms gametophytes are not free living

Nucellus - develops into perisperm that feeds the embryo

Angiosperms

Characteristics:

• Angiosperms have a vascular system

• Angiosperms do not require water for reproduction

• Angiosperm gametophytes are not free living

• Angiosperms are sporophyte dominant

• Angiosperms are heterosporous

• Angiosperms have fruit with seeds

• Angiosperms use animal pollinators

  

Pistil - consists of one or more carpels and consists of an ovary, stigma, and style

Complete flowers have all four basic parts of a flower (sepals, petals, stamens, and carpels)

Incomplete flowers are missing one or more parts that are included on a complete flower (sepals, petals, stamens, and carpels)

Perfect flowers have both male and female part of a flower

Imperfect flowers have only the male or the female part of a flower, not both

Monoecious plants have both male and female imperfect flowers on the same plant

Dioecious plants only bear male or female imperfect flowers

Imperfect flowers are always incomplete, but incomplete flowers are not always imperfect

Fruits and Seeds

The term fruit refers to a mature ovary that contains seeds

Pollination is the process y which pollen is transferred from anther to stigma

Fertilization is the process of fusion of two gametes

The form of a fruit gives an idea about its dispersal. Dry fruits with wings or parachutes may be wind-dispersed, fleshy fruits are often dispersed by animals, explosive fruits can fling seeds, and floating fruits may be water dispersed.

Seeds may remain dormant in soil for long periods of time to ensure that germination occurs in proper conditions

Seeds require moisture and correct temperature to germinate and break dormancy

Fleshy Fruit

Fleshy fruits have three regions of ovary tissue:

1. Exocarp (skin)

2. Mesocarp (fleshy part)

3. Endocarp (directly adjacent to the seed)

   

• Fleshy simple fruits are produced by flowers containing one pistil
• Fleshy aggregate fruits develop from flowers which have more than one pistil
• Fleshy multiple fruits develop from a cluster of flowers known as an inflorescence
• Fleshy accessory fruits are developed from plant parts other than the ovary

Fleshy Simple Fruits

Fleshy simple fruits are divided into berries, hesperidium, pepo, drupes, and pomes

Berries are characterized by the ovary wall becoming fleshy throughout, with examples including tomatoes, grapes, pomegranates, and eggplants

Hesperidium are modified berries in which the outer part of the ovary wall becomes leathery, typically referring to citrus fruits

Pepo is a berry with a relatively thick rind derived from teh receptacle, such as cucumbers, pumpkins, and watermelons

Drupes typically have fleshy mesocarp and a single seep eclosed in a hard pit, such as peaches, almonds, cherries, and mangoes

Pomes have leathery or papery endocarps surrounded by fleshy accessory tissue derived from the floral tube, such as apples and pears

Accessory fruit defines a false fruit also known as a pseudocarp where parts other than the ovary and its wall are important in forming the fleshy fruit

Fleshy Aggregate Fruits

Polydrupes are formed from the development of several simple carples from a single flower, including strawberries and blackberries

Aggregate fruit develops from one flower

Fleshy Multiple Fruits

Multiple fruits are fused fruits that form from an inflorescence, such as mulberries and pineapples

Multiple fruits develop from multiple flowers

Dry Fruits

Dry fruits have all three regions of ovary tissue fused into one layer known as the pericarp

Dry fruits are divided into indehiscent and dehiscent fruits, and further categorized from there

Indehiscent Dry Fruits

Indehiscent dry fruits are characterized by not opening at maturity

They are divided into achene, caryopsis, samaras, and nuts

Achene are small, one-seeded, and characterized by the pericarp and seed being loosely attached, such as sunflowers

Caryopsis are also known as grains and have the fruit wall fused to the seed coat, such as oats, wheat, and corn

Samara have one or more wings, like helicopter seeds from maple and ash trees

Nuts have a hard shell surrounding the seed such as buckeyes, hazelnuts, and acorns

Dehiscent Dry Fruits

Dehiscent dry fruits open at maturity to shed their seeds

They are divided into legumes, follicles, and capsules

Legumes split along both edges and include beans and peas

Follicles split along one edge only, such as milkweed

In capsules the pericarp splits along carpel lines, such as in lilies