Biological Processes: From Cells to Organisms
Goiter and Diabetes
Goiter: Pathological inflammation of the thyroid gland. Diabetes: Disorder in the production of the quantity of insulin needed.
Tropism in Plants
Tropism: Growth responses with which plants react to different external stimuli. Phototropism: Growth toward the light or in the opposite direction. Photojournalism: Variable duration of daylight and darkness in the year. Blooming: Process affected by the photoperiod. Geotropism: The plant’s response to gravity. Thigmotropism: The plant’s response to touch.
Asexual Reproduction
Parthenogenesis: Development of a new being from a single female gamete, a sexual cell that is not fertilized. Asexual Reproduction: Vegetative propagation:
- Binary division: The process of cell division in which a cell originates two daughter cells.
- Fragmentation: Division of the parent’s body to generate a new one with complete individual capacity.
- Budding: Formation of a bud, progenitor cells develop into a new individual.
- Sporulation: Production of spores, which originate new individual cells genetically identical to their parent.
Sexual Reproduction
Sexual Reproduction: Fusion of two gametes (n) from different progenitors (outcrossing), by meiosis, gamete fusion (syngamy).
Fern Life Cycle
The sporophyte phase is dominant. Development: Sporangia release the spores, these form a gametophyte. For this, antheridia and archegonia are developed, the flagellate swims to the antherozoid oosphere and is fruitful, the zygote grows independently of the gametophyte, and develops on the underside of the sori.
Gymnosperm Life Cycle
Development: The plant has ovulated cones, the scales with megasporangia have two ovules, the pollen cone has given microspores by meiosis. Megasporangia produce pollen grains, a grain enters the micropyle and germinates, the megasporocyte is divided into four cells, the gametophyte develops within the megaspore. When the gametes are mature, fertilization occurs a year after pollination, the seed forms and has nutrient reserves.
Angiosperm Life Cycle
Development: Anther has microsporangia and each microsporocyte, the microspores are pollen, the megasporocyte divides by meiosis and produces four megaspores. After pollination, each male gamete discharges into the ovule two nuclei, double fertilization occurs, the zygote develops into an embryo packaged in a seed, when the embryo germinates it forms a sporophyte.
Life Cycles
- Haplontic Cycle: The adult is n, meiosis occurs in the zygote (2n) and four haploid cells originate that develop into individuals (n), algae.
- Diplontic Cycle: The adult is 2n, meiosis occurs in the gonads of adults and gametes are produced (n), after fertilization there is a zygote (2n), protozoa.
- Haplodiplontic Cycle: Alternation of generations, the adult is a sporophyte (2n), and in their sporangia originate meiospores (n) that germinate, forming gametophytes. The zygote is 2n, plants.
Animal Receptors
- Chemoreceptors: Sensitive to various chemical substances, taste and smell have it.
- Mechanoreceptors: They respond to stimuli that involve deformation of the receptor and include touch, pain, and proprioception.
- Photoreceptors: Sensitive to electromagnetic radiation. The eye has it.
- Thermoreceptors: Respond to increased temperature.
- Electroreceptors: Present in some fish, they respond to electromagnetic signals.
Meninges
Membranes that prevent direct contact of nervous tissue with bone. Parts: Pia mater next to the CNS, dura mater in contact with the bone, and the arachnoid is between them.
Embryonic Period
Segmentation: Phases G1 and G2 are avoided, the embryo does not grow but the size of the blastomeres does. After five or six divisions, the morula is formed (embryo 1) and within it the blastocoel. The embryo is in the blastula stage (2nd embryonic state), where if the division is incomplete it is called meroblastic segmentation, and when complete, holoblastic segmentation.
Gastrulation: Morphogenetic processes by which a redistribution of the blastula cells occurs to form an embryo with three cell layers (ectoderm inside, mesoderm in the middle, endoderm outside). It is called a gastrula (3rd embryonic state).
Organogenesis: More localized morphogenetic changes in cells forming germ layers that result in the formation and development of different organs.
Cloning in Mammals
The nuclear transfer technique from a body cell into an egg is the first step. The nucleus of a somatic cell and its DNA has the state that corresponds to the age of the person, so it must be rescheduled. When the core is a younger embryonic cell it is called paracloning. Therapeutic cloning is an attempt to obtain embryonic stem cells from an embryoid structure by transferring a somatic cell nucleus from a patient to an egg from a woman.
Transgenesis in Animals
Introduction of a foreign gene into a genome so that it remains stable and hereditary and affects every cell in the multicellular organism. This is called a transgene and can be made by transgenesis by microinjection of zygotes, or by manipulation of embryonic cells.