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Gibberellin Aj important in stem growth Gibberellin A3 commercially available In 1809, the study of the gibberellins began indirectly with observations of the bakanae, or foolish seedling, disease of rice. Seedlings affected by this disease grow tall more rapidly than their healthy neighbors, but this rapid growth gives rise to spindly plants that die before producing seeds the rice grains used for food . The disease has had considerable economic impacts in several parts of the world. It is...
Parathyroid hormone elevates blood calcium
The parathyroid glands are four tiny structures embedded in the posterior surface of the thyroid gland. Their single hormone product, parathyroid hormone also called PTH or parathormone , is the critical hormone in the regulation of blood calcium levels. Levels of calcium in the blood are sensed by receptors in the plasma membrane of the parathyroid cells. When these receptors are activated, they inhibit the synthesis and release of PTH. A fall in blood calcium levels removes this inhibition...
Steps in Reconstructing Phylogenies
The first step in reconstructing a phylogeny is to select the group of organisms whose phylogeny is to be reconstructed the ingroup and an appropriate outgroup. The next step is to choose the characters that will be used in the analysis and to identify the possible forms of those characters states or traits . A trait may be the presence or absence of a character, or one of the states a particular character may have, such as the number of body segments or number of appendages. The next, and...
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Maternal Fetal capillaries blood pools in intervillus space Maternal Fetal capillaries blood pools in intervillus space needle as the first step of a process called amniocentesis. Cells from the fluid can be cultured and used for biochemical and genetic analyses that can reveal the sex of the fetus, as well as genetic markers for diseases such as cystic fibrosis, Tay-Sachs disease, and Down syndrome. If amniocentesis is performed, it is usually not until after the fourteenth week of pregnancy,...
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Urine leaves the kidney from the inner surface of the medulla and is collected in the ureter. Urine leaves the kidney from the inner surface of the medulla and is collected in the ureter. fytyi 51.9 The Human Excretory System a The human kidneys If fi are positioned in the upper dorsal region of the abdominal V j cavity, ft The human kidney has a regular internal tissue ' structure that is the basis for its function, c The glomeruli and the proximal and distal convoluted tubules are located in...
J Fmamj Jasond
56.5 Rainy and Dry Seasons Change with Latitude In the Tropics and Subtropics, rainy and dry months are highly predictable based on the region's latitude. 56.6 The Circulation of Earth's Atmosphere If we could stand outside Earth and observe its air movements, we would see vertical air circulation patterns similar to those indicated by the black arrows and surface winds similar to those shown by the blue arrows. Both the vertical and horizontal circulation patterns shift to the north during the...
Leaves are the primary sites of photosynthesis
In gymnosperms and most flowering plants, the leaves are responsible for most of the plant's photosynthesis, producing energy-rich organic molecules and releasing oxygen gas. In certain plants, the leaves are highly modified for more specialized functions, as we will see below. As photosynthetic organs, leaves are marvelously adapted for gathering light. Typically, the blade of a leaf is a thin, flat structure attached to the stem by a stalk called a petiole. During the daytime, the leaf blade...
Platelets are essential for blood clotting
Besides producing erythrocytes and leukocytes, the stem cells in the bone marrow produce cells called megakaryocytes. Megakaryocytes are large cells that remain in the bone marrow and continually break off cell fragments called platelets. A platelet is just a tiny fragment of a cell without cell organelles, but it is packed with enzymes and chemicals necessary for its function sealing leaks in blood vessels and initiating blood clotting Figure 49.16 . Damage to a blood vessel exposes collagen...
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A bright light stimulus results in a strong hyperpolarization. opsin pass through several unstable intermediate stages. One of these stages is known as photoexcited rhodopsin because it triggers a cascade of reactions that result in the alteration of membrane potential that is the photoreceptor cell's response to light. To get a better idea of how rhodopsin alters the membrane potential of a photoreceptor cell and how that photoreceptor cell signals that it has been stimulated by light, let's...
The Human Reproductive System
So far we have seen a small sampling of the fascinating diversity of animal reproductive systems. In this section we will describe the structures and functions of the male and female sex organs in mammals specifically, in human beings and discuss hormonal regulation of both male and fe 43.8 The Reproductive Tract of the Human Male The male reproductive organs are shown in front and side views. 43.8 The Reproductive Tract of the Human Male The male reproductive organs are shown in front and side...
Results Lld
Conclusion A diffusible substance from the head region is necessary for molting. 42.3 A Diffusible Substance Triggers Molting The effect of time since the last blood meal on Rhodnius molting experiment 1 led Sir Vincent Wigglesworth to hypothesize that some substance diffusing slowly through the insect's body stimulated molting. Further experiments experiment 2 showed that molting is indeed controlled by a substance a hormone diffusing from the head. ence of a blood meal in the digestive system...
Physiological Regulation and Homeostasis
Homeostasis depends on the ability to regulate the activities of organs and organ systems to keep the internal environment constant. In this section we will discuss the general properties of physiological regulatory systems. In the following sections, we will consider temperature regulation as a specific example. Generally, the activities of organs and organ systems are controlled in other words, sped up or slowed down by actions of the nervous system and the endocrine system. But, to achieve...
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cI cI gene Lysogeny promoter I genes 13.20 Control of Phage X Lysis and Lysogeny Two regulatory proteins, Cro and cl, compete for the operator promoter sites controlling the transcription of genes for viral lysis and lysogeny. Understanding such transcriptional controls can lead to new ways of controlling viral infections. cl accumulates and activates promoters for integration of phage DNA into the host chromosome. The phage enters the lysogenic cycle. cl accumulates and activates promoters for...
SelfQuiz Rxk
1. Smooth muscle differs from both cardiac and skeletal muscle in that a. it can act as a pacemaker for rhythmic contractions. b. contractions of smooth muscle are not due to interactions between neighboring microfilaments. c. neighboring cells are electrically connected by gap junctions. d. neighboring cells are tightly coupled by intercalated discs. e. the membranes of smooth muscle cells are depolarized by stretching. 2. Fast-twitch fibers differ from slow-twitch fibers in that a. they are...
H Hen
By tracing the steps in this manner, they soon discovered a cycle that fixes CO2 in a larger molecule, produces a carbohydrate, and regenerates the initial CO2 acceptor. This cycle was appropriately named the Calvin-Benson cycle Figure 8.13 . The initial reaction in the Calvin-Benson cycle adds the one-carbon CO2 to a receptor, the five-carbon compound ribulose 1,5-bisphosphate RuBP . The product is an inter mediate six-carbon compound, which quickly breaks down and forms two three-carbon...
Soils are complex in structure
Soils are complex systems made up of living and nonliving components. The living components include plant roots as well as populations of bacteria, fungi, protists, and animals such as earthworms and insects Figure 37.2 . The nonliving portion of the soil includes rock fragments ranging in size from large rocks through sand and silt and finally to tiny particles called clay that are 2 im or less in diameter. Soil also contains water and dissolved mineral nutrients, air spaces, and dead organic...
The Archaea
The domain Archaea consists mainly of prokaryotic genera that live in habitats notable for characteristics such as extreme salinity salt content , low oxygen concentrations, high temperatures, or high or low pH. However, many archaea live in habitats that are not extreme. Perhaps the largest number of archaea live in the ocean depths. On the face of it, the Archaea do not seem to belong together as a group. One current classification scheme divides the domain into two principal groups,...
Ratio
Mendel's experiment 1 examined a monohybrid cross Experiment 1 in Mendel's paper involved a monohybrid cross one involving offspring of a cross in which each member of the P generation is true-breeding for a different trait. He took pollen from pea plants of a true-breeding strain with wrinkled seeds and placed it on the stigmas of flowers of a true-breeding strain with spherical seeds Figure 10.2 . He also performed the reciprocal cross by placing pollen from the spherical-seeded strain on the...
Animal Reproduction
Natural selection has created some amazing and bizarre adaptations, but among the most unusual and diverse are the methods that some animals use to reproduce. Just as unmanned submersibles are used in deep-sea exploration, some species of polychaete worms use un-wormed submersibles to reproduce. The adults of these marine worms live in burrows on the seafloor or in coral reefs. Predators make it dangerous for them to leave their burrows to seek a mate, and if they simply released their eggs and...
SelfQuiz Gst
1. Which of the following describes the route of sensory information from the foot to the brain a. Ventral horn, spinal cord, medulla, cerebellum, midbrain, thalamus, parietal cortex b. Dorsal horn, spinal cord, medulla, pons, midbrain, hypothalamus, frontal cortex c. Dorsal horn, spinal cord, medulla, pons, midbrain, thalamus, parietal cortex d. Ventral horn, spinal cord, pons, cerebellum, midbrain, thalamus, parietal cortex e. Dorsal horn, spinal cord, medulla, pons, midbrain, thalamus,...
Three major faunas have dominated life on Earth
The fossil record reveals three great radiations that resulted in the evolution of major new faunas Figure 22.17 . The first one, the Cambrian explosion, took place about 540 mya. The second, about 60 million years later, resulted in the Paleozoic fauna. The great Permian extinctions 300 million years later were followed by the third event, the Triassic explosion, which led to our modern fauna. During the Cambrian explosion, organisms representing all the major body plans of present-day...
Transpiration and the Stomata
The epidermis of leaves and stems minimizes transpirational water loss by secreting a waxy cuticle, which is impermeable to water. However, the cuticle is also impermeable to carbon 36.11 Stomata a A scanning electron micrograph of an open stoma formed by two sausage-shaped guard cells. b Potassium ion concentrations affect the water potential of the guard cells, controlling the opening and closing of stomata. Negatively charged ions accompanying K maintain electrical balance and contribute to...
Tissues Organs and Organ Systems
Cells are the basic building blocks of multicellular animals. When cells with the same characteristics or specializations are grouped together, they form a tissue. There are four basic types of tissues epithelial, connective, muscle, and nervous but there are variations on each basic type. An organ is usually made up of several different tissue types Figure 41.2 . 41.2 Four Types of Tissue All cells can be classified into one of four tissue types. An organ such as the stomach is made up of...
Determining Earths Age
It is difficult to age rocks because any type of rock could have been formed at any time during Earth's history. It is easier to determine the ages of rocks relative to one another. The first 22.1 Young Rocks Lie on Top of Old Rocks The oldest rocks visible in this photo of the Grand Canyon formed about 540 million years ago.The youngest rocks, at the top, are about 500 million years old. 22.1 Young Rocks Lie on Top of Old Rocks The oldest rocks visible in this photo of the Grand Canyon formed...
How does a stationary organism find nutrients
Many heterotrophs can move from place to place to find the nutrients they need. An organism that cannot move, termed a sessile organism, must obtain nutrients and energy from sources that are somehow brought to it. Most sessile animals depend primarily on the movement of water to bring them raw materials and energy in the form of food, but a plant's supply of energy arrives at the speed of light from the sun. However, with the exception of carbon and oxygen in CO2, a plant's supply of nutrients...
Environments and animals can be classified in terms of salts and water
The salt concentration, or osmolarity, of ocean water is about 1,070 milliosmoles liter mosm l , and fresh water is generally between 1 and 10 mosm l. Aquatic environments grade continuously from fresh to extremely salty. Consider a place where a river enters the sea through a bay or a marsh. Aquatic environments within that bay or marsh range in os-molarity from that of the fresh water of the river to that of the open sea. Evaporating tide pools can reach an even greater osmolarity than...
Protists And The Dawn Of The Eukarya 561
While Volvox is colonial and spherical, Oedogonium is mul-ticellular and filamentous, and each of its cells has only one nucleus. Cladophora is multicellular, but each cell is multinu-cleate. Bryopsis is tubular and coenocytic, forming cross-walls only when reproductive structures form. Acetabularia is a single, giant uninucleate cell a few centimeters long that becomes multinucleate only at the end of its reproductive stage. Ulva lactuca is a thin, membranous sheet a few centimeters across its...
V uh Endocytosis and Exocytosis
1 f Macromolecules such as proteins, polysaccharides, and nucleic acids are simply too large and too charged or polar to pass through membranes. This is a fortunate property. Think of the consequences if these molecules could diffuse out of cells A red blood cell would not retain its hemoglobin On the other hand, cells must sometimes take up or secrete intact large molecules. As we saw in Chapter 4, this can be done by means of vesicles that either pinch off from the plasma membrane and enter...
Why dont plants poison themselves
Why don't the chemicals that are so toxic to herbivores and microbes kill the plants that produce them Plants that produce toxic secondary metabolites generally use one of the following measures to protect themselves The toxic material is isolated in a special compartment. The toxic substance is produced only after the plant's cells have already been damaged. The plant uses modified enzymes or modified receptors that do not recognize the toxic substance. The first method is the most common....
What Species Extract Prey From Air
1. In what animal phyla has the ability to fly evolved How do the structures used for flying differ among these animals 2. Extracting suspended food from the water column is a common mode of foraging among animals. Which groups contain species that extract prey from the air Why is this mode of obtaining food so much less common than extracting prey from the water 3. Large size both confers benefits and poses certain risks. What are these risks and benefits 4. Amphibians have survived and...
Dysfunctional enzymes can cause diseases
In 1934, the urine of two mentally retarded young siblings was found to contain phenylpyruvic acid, an unusual byproduct of the metabolism of the amino acid phenylalanine. It was not until two decades later, however, that the complex clinical phenotype of the disease that afflicted these children, called phenylketonuria PKU , was traced back to its molecular phenotype. The disease resulted from an abnormality in a single enzyme, phenylalanine hydroxylase Figure 17.1 . This enzyme normally...
Earths Biogeographic Regions
Explaining species' distributions might seem to be a simple matter, because the question of why a species is or is not found in a certain location has only a few possible answers If a species occupies a particular area, either it evolved there, or it evolved elsewhere and dispersed to the area. If a species is not found in a particular area, either it evolved elsewhere and never dispersed to the area, or it was once present in the area but no longer lives there. Determining which of these...
Chapter Summary Tmr
Living organisms can be divided into three domains Bacteria, Archaea, and Eukarya. Both the Archaea and the Bacteria are prokaryotic the Eukarya constitute the rest of the living world. The Bacteria and the Archaea are less closely related to each other than are the Archaea and the Eukarya. Review Figure 27.2, Table 27.1 The common ancestor of all three domains lived more than 3 billion years ago, and the common ancestor of the Archaea and Eukarya at least 2 billion years ago. See Web CD...
Human brains became larger
The earliest members of Homo sapiens had larger brains than members of the earlier species of Homo. Brain size in the lineage increased rapidly, reaching modern size by about 160,000 years ago. This striking change was probably favored by an increasingly complex social life. The ability of group members to communicate with one another would have been valuable in cooperative hunting and gathering and for improving one's status in the complex social interactions that must have characterized early...
The citric acid cycle produces two CO2 molecules and reduced carriers
Acetyl CoA enters the citric acid cycle from pyruvate oxidation, which has released CO2. At the beginning of the citric acid cycle, acetyl CoA, which has two carbon atoms in its acetyl group, reacts with a four-carbon acid, oxaloacetate, to form the six-carbon compound citrate citric acid . The remainder of the cycle consists of a series of enzyme-catalyzed 7.8 Pyruvate Oxidation and the Citric Acid Cycle Pyruvate diffuses into the mitochondrion and is oxidized to acetyl CoA, which enters the...
Flowering plants have microscopic gametophytes
Before reading this section, you may wish to review the section in Chapter 29 entitled Life cycles of plants feature alternation of generations pages 571-572 . Central to understanding plant reproduction is the concept of alternation of generations, in which a multicellular diploid generation alternates with a multicellular haploid generation. In angiosperms, the diploid sporophyte generation is the larger and more conspicuous one. The sporophyte generation produces flowers. The flowers produce...
Changes In Cell Structure And Function
Other early steps in the evolution of the eukaryotic cell are likely to have included three advances the formation of ribosome-studded internal membranes, some of which surrounded the DNA see Figure 28.3 the appearance of a cytoskeleton and the evolution of digestive vesicles. A cytoskeleton made up of actin fibers and microtubules would allow the cell to manage changes in shape, to distribute daughter chromosomes, and to move materials from one part of the now much larger cell to other parts....
. Negative Feedback A. Is Not As Common As Positive Feedback In Regulatory
1. If the Q10 of the metabolic rate of an animal is 2, then a. the animal is better acclimatized to a cold environment than if its Q10 is 3. c. the animal consumes half as much oxygen per hour at 20 C as it does at 30 C. d. the animal's metabolic rate is not at basal levels. e. the animal produces twice as much heat at 20 C as it does at 30 C. 2. Which statement about brown fat is true a. It produces heat without producing ATP. b. It insulates animals acclimatized to cold. c. It is a major...
For Discussion Bsn
1. In Chapter 47, we will see that the functioning of muscles requires calcium ions to be pumped into a subcellular compartment against a calcium concentration gradient. What types of molecules are required for this to happen 2. Some algae have complex glassy structures in their cell walls. These structures form within the Golgi apparatus. How do these structures reach the cell wall without having to pass through a membrane 3. Organisms that live in fresh water are almost always hypertonic to...
Choanoflagellates
One group of heterotro phic protists with flagella, the choanoflagellates, is thought to comprise the closest relatives of the animals. The choanoflagellates are sister to the animals, and the animal-choanoflagellate lineage is sister to the fungi see Figure 28.9 The clade consisting of fungi, animals, and choanoflagellates is called the opisthokonts. 28.28 A Link to the Animal Kingdom Choanoflagellates may be close relatives of the sponges, and thus represent a link between the protists and...
Q 2q 1q 1q 3 S 22 2q
Minisatellites are 12-100 base pairs long and are repeated several thousand times. Because DNA polymerase tends to make errors in copying these sequences, the number of copies present varies among individuals. For example, one person might have 300 minisatellites and another, 500. This variation provides a set of molecular genetic markers that can be used to identify an individual. Microsatellites are very short 1-5 bp sequences, present in small clusters of 10-50 copies. They are scattered...
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was discovered to be necessary for this conditioned reflex. Thus, it was possible to localize learning to an identifiable set of synapses in the mammalian brain. memory. Attempts to treat human neurological diseases have led to the localization of areas of the brain involved in the formation and recall of memories. Epilepsy is a disorder characterized by uncontrollable increases in neuronal activity in specific parts of the brain. The resulting seizures, or epileptic fits, can endanger the...
Cleavage Repackaging the Cytoplasm
The transformation of the diploid zygote into a mass of cells occurs through a rapid series of cell divisions, called cleavage. Because the cytoplasm of the zygote is not homogeneous, these first cell divisions result in the differential distribution of nutrients and cytoplasmic determinants among the cells of the early embryo. In most animals, cleavage proceeds with rapid DNA replication and mitosis, but no cell growth and little gene expression. The embryo becomes a solid ball of smaller and...
Sex Determination and SexLinked Inheritance
In Mendel's work, reciprocal crosses always gave identical results it did not matter, in general, whether a dominant allele was contributed by the mother or by the father. But in some cases, the parental origin of a chromosome does matter. For example, as we saw at the beginning of this chapter, human males inherit hemophilia A from their mother, not from their father. To understand the types of inheritance in which the parental origin of an allele is important, we must consider the ways in...
Deuterostomes and Protostomes Shared Evolutionary Themes
The evolution of deuterostomes paralleled the evolution of protostomes in several important ways. Both lineages exploited the abundant food supplies buried in soft marine substrata, attached to rocks, or suspended in water. Many groups of both lineages developed elaborate structures for moving water and extracting prey from it. In some lineages of both groups, the body cavity became divided into compartments that allowed better control of shape and movement. Some members of both groups evolved...
ttfvh Why Three Domains
1 What does it mean to be different You and the person nearest you look very different certainly you appear more different than the two cells shown in Figure 27.1. But the two of you are members of the same species, while these two tiny organisms that look so much alike actually are classified in entirely separate domains. Still, all three of you you in the domain Eukarya and those two prokaryotes in the domains Bacteria and Archaea have a lot in common. Members of all three domains replicate...
Passive Processes ofMembrane Transport
We have examined membrane structure and how it is used to perform one major membrane function the binding of one cell to another. Now we turn to the second major membrane function the ability to allow some substances, but not others, to pass through the membrane and enter or leave a cell or organelle. This characteristic of membranes is called selective permeability. There are two fundamentally different kinds of processes by which substances cross biological membranes to enter and leave cells...
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.and resulting in a nonfunctional mRNA and or protein. .and resulting in a nonfunctional mRNA and or protein. 14.3 DNA Transposons and Transposition At the end of each DNA transposon is an inverted repeat sequence that helps in the transposition process. If a transposon replicates not just itself but also an adjacent gene, the result may be a gene duplication. A transpo-son can carry a gene, or a part of it, to a new location in the genome, shuffling the genetic material and creating new genes....
The seed germinates and forms a growing seedling
All developmental activity may be suspended in a seed, even when conditions appear to be suitable for its growth. In other words, a seed may be dormant. Cells in dormant seeds do not divide, expand, or differentiate. For the embryo to begin developing, seed dormancy must be broken. As the seed begins to germinate to develop into a seedling it first takes up water. The growing embryo must then obtain chemical building blocks monomers for its development by digesting the polysaccharides, fats,...
Autoregulation matches local blood flow to local need
The autoregulatory mechanisms that adjust the flow of blood to a tissue are local mechanisms, but they can be influenced by the nervous system and by certain hormones. Blood flow through a capillary bed is controlled by the constriction of smooth muscle in the arteries and arterioles. 49.17 Local Control of Blood Flow Low O2 concentrations or high levels of metabolic by-products cause the smooth muscle of the arteries and arterioles to relax, thus increasing the supply of blood to the capillary...