Cellular Reproduction and Biological Development: A Comprehensive Study
**Asexual Reproduction**
- Occurred 3500 million years ago
- Involves mitosis
- One progenitor
- Normal cells
- Simple and profitable reproduction system
- Genetically identical individuals
- Recombination of genes, not characters
- Rapid growth in the number of individuals
**Sexual Reproduction**
- Occurred 1500 million years ago
- Involves meiosis
- Almost always two parents
- Special cells
- Constructive and very complicated reproductive expenditure
- Genetically different individuals
- Easy recombination of genes and characters
**Parthenogenesis**
Sexual reproduction variant, from egg to embryo, can develop without fertilization.
**Twins**
- Dizygotic twins: Two or more eggs fertilized simultaneously by different sperm.
- Monozygotic twins: One ovum fertilized by one sperm, cell groups formed two separate, genetically identical individuals.
**Pollen and Pollination**
Pollen originates in the stamens in the anthers. It is formed by a double membrane: resilient, and species-specific. Features a vegetative cell and a generative cell. The generative cell leads the pollen tube during germination. The mobile spermatic fertilizes the ovule.
- Direct: Autogamous plant: pollen falls on the stigma of the same flower.
- Indirect: Allogamous: pollen from one flower falls on the stigma of another flower.
**Assisted Reproduction**
Artificial insemination, in vitro fertilization, embryo transfer.
**Life Cycles**
- Haplontic: The zygote undergoes meiosis immediately after dividing. One set of chromosomes. Found in fungi and algae.
- Diplontic: Meiosis occurs immediately before gamete formation (gametogenesis). Found in humans and animals. Sperm and ova.
- Diplohaplontic: Combines the advantages of the two.
**Mosses**
The sporophyte, in which meiosis occurs, passes to the sporangium where eggs are released as spores, which fall and give rise to the protonema, which gives rise to the gametophyte (which can be male or female), producing antheridia or archegonia. The antherozoid exits and moves through the water to the archegonium, where the sporophyte starts the cycle all over again.
**Ferns**
In the sporangium, eggs are released as spores. The spores are the gametophyte, which can be divided into antheridia or archegonia. The antherozoid travels through the water and fertilizes the ovule, and finally, the sporophyte undergoes meiosis and starts again.
**Medusa**
Adult medusa produces gametes that originate a swimming larva that is fixed to the bottom as a polyp. The polyp undergoes strobilation and develops into a new adult jellyfish.
**Flowering Plants**
Predominance of the sporophyte. The pollen tube is now the gametophyte but with few cells above the sporophyte. Everything happens within the flower.
**Fungi**
Reproduce asexually by spores or sexually. When sexual reproduction occurs, they become haploid hyphae that can merge and form a diploid cell.
**Protoctists**
Variety of biological cycles.
**Monera**
They do not have a nucleus; they do not need meiosis to restore genetic material.
**Embryological Process**
Embryology studies zygote development.
- Cell proliferation: Increased number of cells by multiplication.
- Cellular differentiation: Modification of structure and cellular function with specialized formation.
- Morphogenesis: Appearance of the embryo’s shape and differentiation growth.
**Gastrulation**
Phases that determine the basic appearance of the adult organism. Cellular morphogenesis occurs, and the blastocoel sinks in. There are two layers of cellular structures, the archenteron (or small intestine) which connects to the outside through the blastopore (anus).
**Germ Layers**
- Ectoderm: Epidermis, nails, nervous system, sweat glands, enamel.
- Mesoderm: Dermis, connective tissue, cartilage, bone, muscles, blood, gonads, kidneys.
- Endoderm: Mucous membranes of the digestive tract, bronchi, lungs, urethra, pancreas, liver, thymus, thyroid.
**Postembryonic Development**
- Direct: Born with a long period of development of embryonic organs.
- Indirect: Born and shaped as a larva before becoming an adult or undergoing metamorphosis to become an imago.
**Metamorphosis**
- Simple: Common in insects and other animals, the larva resembles the adult, does not go through a period of inactivity, and does not stop feeding during development.
- Complete: Larvae go through a pupa or chrysalis stage before adulthood.
**Vegetable Development**
Embryonic cells (meristems remain in continuous development) and seed germination. Seeds are formed from fertilized eggs.
Seed parts: Embryo, endosperm, and episperm.
Embryo parts: Plumule (stem), radicle (primary root), and cotyledons. Embryo development can be held (sleep or latency). The ideal way of life is latent active life.
- Epigeal germination: Cotyledons emerge and accompany the stem in its ascent.
- Hypogeal germination: Cotyledons remain inside the seed.
**Levels of Organization**
- Molecular: The bioelements that combine to form biomolecules are studied.
- Cell: Structure, function, and reproduction.
- Organism: How it is coordinated. Unicellular, multicellular, organs and tissues are present.
- Population: Organisms as constituents of a population.
- Ecosystem: Interrelationships between organisms and the environment in which they live.
**Bioelements**
Chemical elements that enter the composition of living matter and the necessary functions for the organism: Hydrogen, oxygen, carbon, nitrogen, phosphorus, sulfur, sodium, potassium, calcium, magnesium, and chlorine.
**Water**
- Intracellular: Liquid parts of cells.
- Interstitial: Space between cells.
- Circulating: Organic liquids.
- Metabolic: Biological reactions.
Functions: Good solvent, transports many substances, facilitates chemical reactions and metabolism, excellent temperature regulation, maintenance of cell structure and shape.
**Mineral Functions**
Structural, pH regulators, stabilizers, osmotic regulatory processes, specific.
**Proteins**
Formed by carbon, hydrogen, oxygen, and nitrogen, also called protides, they are polypeptides, peptide chains of amino acids linked together. When they undergo alterations in structure, properties, and chemical function, it is called denaturation.
- Holoproteins: Formed by amino acids.
- Conjugated mixtures: Prosthetic groups are diverse in chemical nature.
**Biological Functions of Proteins**
Structural and protection, catalytic, conveyor, nutrient availability and regulation, hormone, contraction, defense and reconnaissance, homeostatic.
**Structure of Proteins**
- Primary: Or sequence, indicating when the amino acid forms and the order in which they are bound by a peptide group between the amino and carboxyl groups.
- Secondary: Disposition in space of the primary structure. Alpha helix and beta-sheet, drawing: coiled phone cord.
- Tertiary: Bending of the secondary structure. What position the amino acids occupy in space. Conformations:
- Fibrous: (like a rope, stable, hard, and insoluble in the cellular environment, placed in the form of parallel plates forming [keratin, elastin, collagen, gelatin])
- Globular: (cabbage, soluble in the biological environment and of high nutritional value [histone, prolamins, albumin])
- Heteroproteins: Formed by a prosthetic group (glycoproteins, lipoproteins, phosphoproteins, nucleoproteins, chromoproteins)
- Quaternary: Proteins formed by two or more polypeptide chains.