Botany Exam 4

Chapter 9: Flowers and Reproduction

• Asexual Reproduction produces genetically identical offspring, advantageous in stable environments, allowing for rapid colonization, and enabling reproduction by isolated individuals. However, it is vulnerable to habitat changes.
• Sexual Reproduction produces genetically diverse offspring, some potentially better adapted to new conditions; however, it is slower to colonize and requires interaction between individuals.

Reproduction Process

• Meiosis in flowers occurs in anthers and ovules, creating haploid spores (microspores and megaspores). Microspores develop into male gametophytes (pollen), while megaspores develop into female gametophytes (embryo sac).
• Pollen, the male gametophyte, germinates, forming a pollen tube and carrying two sperm nuclei.
• The female gametophyte, housed within the ovule, contains an egg, antipodals, synergids, and polar nuclei.

Asexual Reproduction Methods

• Fragmentation, a common method, involves plant parts becoming independent individuals.

Sexual Life Cycle of Plants

• Sporophytes are diploid and produce haploid spores.
• Gametophytes produce gametes through mitosis, and syngamy forms a diploid zygote.

Flower Structure

• Complete flowers have sepals, petals, stamens, and carpels.
• Sepals protect flower buds.
• Petals attract pollinators.
• Stamens produce pollen.
• Carpels contain the ovary, style, and stigma.

Pollination and Fertilization

• Pollination is pollen transfer to the stigma.
• Fertilization in angiosperms is double fertilization, combining sperm and egg.

Embryo and Seed Development

• The zygote forms the embryo.
• Cotyledons store nutrients.
• The seed coat develops from integuments.

Fruit Development

• The ovary matures into the fruit.
• Fruit layers include the exocarp (outer), mesocarp (middle), and endocarp (inner).

Cross-Pollination vs. Self-Pollination

• Cross-pollination involves pollen from a different plant.
• Self-pollination involves pollen from the same flower or plant.

Pollination Mechanisms

• Animal pollination relies on coevolution with animals.
• Wind pollination features lacking petals, large stigmas, and many pollen grains.

Fruit Types and Seed Dispersal

• True fruits contain only ovarian tissue.
• Accessory fruits include non-ovarian tissue.
• Seed dispersal occurs through wind, water, or animals.

Chapter 13: Soils and Mineral Nutrition

• Plant metabolism relies on sunlight, water, air, and soil obtained from minerals, used directly, or as part of compounds.
• Soil components include abiotic minerals, water, and air; biotic flora, fauna, and microbes, which supply minerals, hold water, provide air, and stabilize plants.

Essential Elements

• Hydroponic solutions help identify essential elements, classified as macro and micro elements.
• Essential elements are necessary for development, have no substitutes, and act within the plant.

Mineral Deficiency

• Excess minerals harm plants, especially in desert soils or with aluminum toxicity.
• Deficiency causes diseases, common in nonnative plants, with symptoms like chlorosis (yellow leaves), anthocyanin accumulation (purple leaves), and necrosis (dead tips/margins).

Soil and Mineral Availability

• Weathering (physical and chemical) releases minerals from rocks.
• Soil texture influences water retention and mineral availability.
• Cation exchange (CE) involves roots absorbing cations, affected by soil acidity and pH.

Mycorrhizae

• Mycorrhizae are a symbiotic relationship between roots and fungi, aiding plant phosphorus absorption.

Nitrogen Metabolism

• Nitrogen fixation converts N2 gas to usable forms.
• Reduction converts nitrate to ammonium.
• Assimilation incorporates ammonium into organic compounds.
• Symbiotic nitrogen-fixing bacteria are used by plants.

Storage of Minerals

• Plants store minerals in vacuoles, sometimes polymerized in seeds.

Chapter 12: Meiosis and Alternation of Generations

• Asexual reproduction creates identical cells.
• Sexual reproduction is common in plants, resulting in seeds, and involves gametes (egg and sperm), forming a zygote.

Chromosomes and Meiosis

• Chromosomes consist of two sets from parents.
• Homologous chromosomes are identical in length, DNA, genes, and centromere location.
• Meiosis produces four cells with half the parent's chromosome number, and genetically diverse cells.

Phases of Meiosis

• DNA replicates before Meiosis.
• Meiosis I halves chromosome number.
  • Prophase I: chromosome condensation, pairing, crossing-over.
  • Metaphase I: chromosomes align at the equator.
  • Anaphase I: chromosome separation to poles.
  • Telophase I: cell division into two.
• Meiosis II does not reduce the chromosome number.
  • Prophase II: chromosome condensation
  • Metaphase II: chromosome alignment
  • Anaphase II: chromatid separation
  • Telophase II: cell division into four cells.

Alternation of Generations

• Haploid (1x) has one set of chromosomes (gametes).
• Diploid (2x) has two sets of chromosomes (zygote).
• Polyploid has more than two sets.

Life Cycle

• Sporophytes develop from zygotes and produce spores through meiosis.
• Gametophytes develop from spores and form gametes through mitosis; fertilization creates a zygote.

Organisms with Alternation of Generations

• Alternation of generations is observed in protists, fungi, and plants; most evident in plants.

Rules for Alternation of Generations

• Gametophyte generation begins with a spore and ends with a gamete, and has half the sporophyte's chromosomes.
• Sporophyte generation begins with a zygote, and ends with a sporocyte, having twice the gametophyte's chromosomes.
• Transitions occur via meiosis (sporophyte to gametophyte) and fertilization (gametophyte to sporophyte).

Chapter 15: Evolution

• Natural Selection is the principle that organisms with favorable traits survive better and reproduce more successfully. This was proposed by Charles Darwin in 1859.
• Organic Evolution describes genetic changes in populations over time. Evolutionary concepts are used in medicine, agriculture, forensics, biotechnology, economics, and law.

Evolution in Agriculture

• Artificial Selection involves humans selectively breeding plants and animals for desired traits, as seen with the domestication of tomatoes.
• Agricultural systems can influence the evolution of native species, like developing insect resistance to pesticides.

Evolutionary Medicine

• Evolutionary principles are applied to treat diseases; for example, bacteria evolving resistance to antibiotics.

Species Extinctions and Invasions

• Conservation biology utilizes evolutionary principles to study species changes.
• Invasive species, like Kudzu, can displace native species.

Biotechnology and Evolution

• Transgenes, foreign genes in engineered crops, can potentially exchange with wild relatives, potentially leading to herbicide-resistant weeds.

Early Development of Evolutionary Concepts

• Aristotle arranged organisms from simple to complex.
• Leonardo da Vinci recognized fossils as remains of extinct organisms.
• Lamarck's concept included the inheritance of acquired characteristics.

Epigenetics

• Epigenetics studies heritable changes in gene expression, not due to mutation; these are often reversible and passed to subsequent generations.

Revolutions in Thought

• The first evolutionary thought revolution was Darwin's natural selection theory.
• The second involved integration with Mendelian genetics and population genetics.
• The third revolution includes "Evo-devo," focusing on development evolution and homeobox genes.

Charles Darwin

• Darwin's voyage on the HMS Beagle collected evidence influencing his views, including Malthus's population ideas.
• He presented evidence from homology, convergent evolution, fossils, and biogeography.

Microevolution

• Microevolution involves changes within species due to natural selection, mutations, migration, and genetic drift.
• Darwin's observations applied to artificial selection and competition also apply.

Principles of Natural Selection

1. Overproduction of offspring.
2. Struggle for existence.
3. Inheritance of favorable traits.
4. Survival and reproduction of the fittest.

Mutation and Migration

• Mutation is a change in genes or chromosomes.
• Migration involves gene flow between populations.

Rates of Evolution

• Punctuated Equilibrium describes bursts of major change followed by periods of minor change.

Macroevolution

• Macroevolution details how species evolve, including geographic, ecological, and mechanical isolation.

Role of Polyploidy

• Polyploidy, doubling of chromosome number, is common in plants, leading to new species.

Hybridization

• Hybrids, offspring from different parents, can lead to new gene combinations.

Alloploidy and Autoploidy

• Allopolyploidy results from interspecific hybridization.
• Autopolyploidy arises within a single species.

Apomixis

• Apomixis is asexual reproduction producing seeds without fertilization; an example is dandelions.

Discussion

• The origin of life was viewed by some early thinkers as stemming from a divine creator, while incomplete evidence requires different interpretations.

Chapter 13: Genetics and Molecular Biology

• Transposable elements, described by Barbara McClintock, are genes that move within a chromosome.

Molecular Genetics

• DNA Structure: DNA consists of nucleotides: nitrogenous base, deoxyribose sugar, and phosphate group.
• Four bases include Adenine (A), Guanine (G), Cytosine (C), and Thymine (T); A pairs with T, and G with C.
• DNA functions include storage, replication, and expression (transcription into RNA and translation into protein).
• RNA types include mRNA (messenger), tRNA (transfer), and rRNA (ribosomal).
• The genetic code uses codons (three-nucleotide sequences) on mRNA. 64 codons code for 20 amino acids.
• Mutations are DNA sequence alterations caused by mutagens like UV light, radiation, and chemicals.

Cytogenetics

• Chromosome structure changes include inversions (segments reversed) and translocations (segments moved).
• Chromosome number changes include aneuploidy (extra or missing chromosomes) and polyploidy (extra sets).

Mendelian Genetics

• Gregor Mendel, studying inheritance in pea plants, established the monohybrid and dihybrid crosses.
• Mendelian laws include unit characters (traits controlled by allele pairs), dominance (dominant alleles mask recessive), and independent assortment (different traits segregate independently, influencing traits).
• Crosses include backcrosses (hybrid with parent) and testcrosses (dominant with homozygous recessive).
• Incomplete dominance produces an intermediate phenotype in the heterozygote.

Gene Interactions

• Genotype influences phenotype; functional proteins are usually associated with dominant alleles, and often recessive alleles are non-functional.
• Quantitative traits have a range of phenotypes, like fruit yield.

Extranuclear DNA

• Mitochondria and chloroplasts have DNA inherited maternally.

Linkage and Mapping

• Linked genes are close on a chromosome, and crossing-over frequency helps map genes.

Hardy-Weinberg Law

• Genetic equilibrium describes stable allele frequencies in large random-mating populations without external forces.

Chapter 11: Growth and Development

• Growth is an irreversible increase in mass through cell division and enlargement. Growth can be determinate (single season) or indeterminate (long-term).
• Differentiation is the development of cells with specialized functions.
• Development involves coordinating growth and differentiation into tissues and organs, influenced by genes and the environment.

Nutrients, Vitamins, and Hormones

• Nutrients provide energy and essential elements, obtained from the environment.
• Vitamins are organic molecules essential for catalyzed reactions, needed in small amounts.
• Hormones are produced in growing parts and regulate plant development, functioning in small amounts and acting through signal transduction pathways.

Plant Hormones

• Five major classes include Auxins (promote enlargement and root initiation), gibberellins (stimulate growth and flowering), cytokinins (stimulate cell division), abscisic acid (inhibits other hormones), and ethylene (promotes ripening and abscission).

Hormonal Interactions

• Apical dominance suppresses lateral bud growth.
• Senescence is cell component breakdown leading to death, regulated by hormones.

Plant Movements

• Growth movements are caused by unequal growth rates in parts (nodding).
• Turgor movements depend on internal water pressure; pulvini are involved.
• Taxic movements are entire plant or cell movements toward/away from stimuli.

Photoperiodism

• Photoperiodism is the response to day/night length.
• Different plant types (short-day, long-day, day-neutral) respond differently to light periods.

Phytochromes and Cryptochromes

• Phytochromes are light-sensitive pigments with two forms (Pr and Pfr) involved in photoperiodism.
• Cryptochromes are blue light-sensitive pigments involved in circadian rhythms.

Temperature and Growth

• Thermoperiod is the optimal night/day temperatures for growth; lower nighttime temps can increase sugar content and root growth.

Dormancy and Quiescence

• Dormancy is growth inactivity.
• Quiescence is delayed germination until environmental conditions are favorable.
• Stratification is used to break dormancy artificially.