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the process by which animals control solute concentrations and balance water gain and loss.
Water balance, electrolyte balance, and excretion of waste products are tightly integrated processes.
the total solute concentration of a solution, measured as moles of solute per liter of solution.
be isoosmotic with the surrounding environment. Most marine animals (marine sponges, jellyfish, mollusks, and echinoderms)
control the internal osmolarity independent of the surrounding environment.
When they migrate to the ocean:
When in rivers and streams:
the process that rids the body of nitrogenous metabolites and other metabolic waste products.
In vertebrates, urea is produced by the liver as a combination of carbon dioxide and ammonia.
The main disadvantage of urea is its energy cost – energy must be expended to produce urea from ammonia.
Evolution of this efficient water conservation mechanism is a key adaptation that allowed insect ancestors to transition from aquatic to terrestrial habitats and diversify.
only reach a short distance into the medulla.
extend from the cortex deep into the medulla.This nephron type is essential for producing urine that is hyperosmotic to body fluids (high in solutes, low in water), which is key for water conservation
Reabsorption & Secretion:
ADH makes the kidney transport epithelium in the collecting ducts more permeable to water by activating aquaporins – this results in more water being reabsorbed back into the body to return blood osmolarity back to the set point.
Eating salty foods or losing water through sweating causes blood osmolarity to increase (i.e. high blood solute concentration) – this triggers the hypothalamus to release ADH into the bloodstream.
High water intake would have the opposite effect – a decrease in blood osmolarity would trigger the hypothalamus to stop the release of ADH. This would deactivate aquaporins in the collecting ducts so that more water is lost in the urine and blood osmolarity is brought back up within normal range.
Sexual reproduction involves the fusion of gametes (fertilization).
Asexual reproduction is the generation of new individuals without fusion of egg and sperm.
sexual reproduction results in offspring that are genetically different from each other and from their parents.
Asexual reproduction = genetically identical offspring
development of an egg without fertilization.
variation in offspring genotypes and phenotypes that results from genetic recombination, which may be important in the face of such factors as rapidly changing environments or evolving pathogens.
Daphnia, reproduce asexually via parthogenesis when conditions are favorable and reproduce sexually when conditions are poor
Spermatogenesis occurs continuously throughout puberty and adulthood while the number of gametes a female will produce is currently thought to be determined before birth.
Oogenesis has long interruptions between steps while spermatogenesis occurs in a continuous sequence
In many animal species, individuals release their gametes into their environment, and external fertilization occurs.
In other animals, males deposit sperm into the reproductive tracts of females and internal fertilization occurs.
Most animals that rely on external fertilization live in moist or aquatic environments and tend to produce large numbers of gametes.
Gametogenesis occurs in response to environmental cues such as lengthening days and warmer water temperatures, which indicate a favorable season for breeding.
Internal fertilization is an adaptation that enables sperm to reach an egg efficiently, even when the external environment is dry (e.g. terrestrial habitats).
This type of fertilization typically requires cooperative behavior that leads to copulation.
In oviparous animals, the egg is laid outside the mother's body and the embryo develops in the external environment.
placenta of mammals and some fish) or via oophagy or intra-uterine cannibalism (some sharks).
In ovoviviparity, offspring develop inside the parent’s body but are nourished by nutrient-rich yolk stored in the egg.
Stomach brooding frogs, male seahorses
secrete the gonadotropins – follicle stimulating hormone (FSH) and lutenizing hormone (LH).
FSH and LH regulate gametogenesis directly by targeting tissues in the gonads, and indirectly by regulating sex hormone production.
Development of the reproductive tract in embryos.
Maturation of the reproductive tract and secondary sex characteristics during the transition from childhood to adulthood.
Regulation of spermatogenesis and oogenesis in adults.
The uterine lining (endometrium) undergoes a dramatic thickening in preparation for possible implantation of an embryo.
LH stimulates the follicular tissue left behind after ovulation to transform into a glandular structure called a corpus luteum and begin secreting estradiol and progesterone.
This causes a spike in FSH and LH levels because estradiol exerts positive feedback on FSH and LH at high levels by increasing GnRH levels.d progesterone.
Near the end of the luteal phase, low gonadotropin (FSH, LH) levels cause the corpus luteum to disintegrate.
the cessation of ovulation and menstruation, occurs when the ovaries lose their responsiveness to FSH and LH – resulting in a decline in estradiol production.
regulates testosterone and other androgen production by Leydig cells, which are located around the exterior of the seminiferous tubules – this promotes spermatogenesis in the tubules.
promotes the activity of Sertoli cells, which are found within the seminiferous tubules and nourish the sperm.
formation of gametes (egg and sperm) in adult animals.
fusion of egg and sperm, which forms a zygote.
contains the nucleus and the enzyme-filled acrosome, which allows the sperm to penetrate the egg's barriers.
encloses a centriole, which will fuse with a second centriole that is contributed by the egg, to form the centrosome.
The relatively large size of egg cells is due to the nutrient storage that is required for early embryonic development.
Egg-laying species produce much larger eggs; the yolk of the egg is the embryo’s sole source of nutrition prior to hatching
Many eggs contain cortical granules, small enzyme-filled vesicles that are activated during fertilization.
The eggs of many species also contain cytoplasmic determinants (RNA or proteins) that control the early events of development.
fertilization by more than one sperm.
After fertilization, a calcium (Ca2+) -based signal (released from endoplasmic reticulum inside the egg cell) is rapidly induced and propagated throughout the egg, resulting in the formation of a fertilization envelope, which keeps away additional sperm.
involves the initiation of metabolic reactions and cell cycle processes that trigger the onset of embryonic development following fertilization.
involves the first steps in the formation of the brain and spinal cord in vertebrates.
As the somite matures, somite cells become irreversibly determined, and will eventually differentiate into a specific cell type based on their location within the somite.
During the process of determination, somite cells respond to signals from nearby tissues.
These signals diffuse away from cells in the notochord, the neural tube, and nearby ectoderm and mesoderm to act on specific populations of target cells in the somite, resulting in determination then differentiation of the somite cells.
are proteins and RNA that are found in specific locations within the egg cytoplasm, so they end up in specific populations of blastomeres.
,The expression of different genes in different cell types, is key to cell differentiation during development.
A gene can be regulated at multiple levels:
In Drosophila embryos, the bicoid protein is a regulatory transcription factor that forms a concentration gradient and provides cells with information about their position along the anterior-posterior axis.
Anterior cells receive a high concentration of bicoid protein, the posterior cells receive a low concentration.
the series of events that determine the spatial organization of an embryo.
Certain early signals act as master regulators, setting up the major body axes of the embryo.
These master regulators activate a network of genes that send signals with more specific information about the spatial location of cells, activating genes that specify finer and finer control over what a cell becomes .
Regulatory genes act in a sequence, triggering gene cascades that provide progressively detailed information about where cells are located in time and space.
An example of a group of genes in this tool kit is the Hox gene cluster, which includes transcription factors that function in patterning the body axis.
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