Biology 1120 bios 1120
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Date Created: 04/18/16
1 BIOS 1120 UNIT 3 EXAM STUDY GUIDE Chapter 28 28.1 Matter cycles and energy are continually exchanged between the living and non-living components of the environment All ecosystems consist of biotic (living) components (e.g. bacteria, plants, animal and fungi) and abiotic (non-living) components (e.g. climate, temperature, light, water and minerals in the soil) 28.2 Energy flows in ecosystems Energy makes a one way journey through ecosystems. Radiant energy from the sun is captured by the process of photosynthesis into chemical energy for use by plant cells, and thereby indirectly made available as a source of energy for other organisms. Ecologists study ecosystems in terms of trophic levels. Autotrophs (e.g. plants) make their own food and are referred to as producers because their activities make energy available for other organisms in the ecosystem. Heterotrophs (e.g. animals, bacteria) are organisms that get their energy from other organisms, and are referred to as consumers because they use energy taken from producers or other consumers. Food chains depict the flow of energy linearly from producers to consumers; food webs draw attention to the fact that organisms may be part of more than one food chain and have different roles. Decomposers and detritovores play a particularly important role in ecosystems, because they breakdown the remains of organisms (which they use as a source of food), returning nutrients back to the abiotic environment The flow of energy between trophic levels is very inefficient, because with each conversion, part is converted to heat energy that is no longer usable. Biological magnification refers to the fact that because consumers at higher trophic levels must eat many times their own weight in order to live, trace toxic substances such as mercury tend to accumulate in their tissues 28.3 Matter cycles in ecosystems In contrast to energy, matter endlessly cycles between biotic and abiotic components of the environment. Atoms enter and leave associations with other atoms as molecules are formed and broken down, but at a fundamental level the atom is never changed by these interactions. The living world is composed primarily of macronutrients (oxygen, carbon, hydrogen, nitrogen, phosphorus), and micronutrients (trace amounts of other minerals, e.g. iron). The hydrological (water) cycle is driven by solar energy, only a small fraction of water is part of the living world. The movement of other macronutrient cycles is driven largely by the activities of living organisms. 28.4 Human activities disrupt nutrient cycles 2 Human activities, particularly the burning of fossil fuels and the large scale use of fertilizers, play a particularly disruptive role. Chapter 26 26.1 Ecology is the study of the interactions between a population and the abiotic and biotic components of the environment. Populations consist of all members of a particular species within an ecosystem; communities consist of multiple species that cohabitate in a given area. Changes in the size of a population may reflect its natural rate of increase (r), immigration, emigration, birth and death rates. Exponential growth occurs whenever a constant rate of growth occurs and is depicted by a J-curve. 26.2 Population growth is limited by environmental resistance Environmental resistance refers to all curbs on a population’s growth, including biotic factors (e.g. predators, competitors) and also abiotic factors (e.g. freezing weather, droughts). Density-independent: limits population regardless of its density (e.g. weather); Density-dependent: effectiveness increases as density of population rises (e.g limited availability of nutrients, predators, communicable diseases) 26.3 Populations vary in how they are distributed in space and age. Spatial distributions can be clumped, uniform or random. Age distributions can be characterized as late-loss, constant loss or early loss. 26.4 Human population growth continues to be rapid During the past few hundred years, human population growth has been exponential, owing to advances in technology, agriculture and medicine. This rapid growth is not uniform. In developed countries, birth rates are declining; developing countries, in contrast, have much higher birth rates The age structure of a population is useful in predicting future growth The demands human population growth are placing on the planet are unsustainable Chapter 14 14.1 Early biological thought did not include the concept of evolution. Evolution refers to a change in the characteristics of a population over time. Species were once believed to be created simultaneously by God at one time. Voyages of discovery and a growing recognition that the earth is ancient and fossils represent organisms that no longer exist led scientists to speculate that live had evolved. Darwin and Wallace proposed a plausible mechanism for how evolution has occurred: natural selection. 14.2 Natural selection requires four factors 3 1. Organisms in a population vary in ways that affect their ability to survive and reproduce; 2. Some of these differences are inheritable; 3. Not all who are born survive to adulthood and reproduce; and 4. The likelihood an organism survives and reproduces is not due to chance alone. 14.3 There is abundant evidence that evolution has occurred. The fossil record includes evidence of intermediate forms for those organisms with hard body parts. Comparative anatomy indicates similarities among modern organisms that represent modified versions of more basic ancestral plans. Homologous structures (similar structures that may have different functions) are evidence of common ancestry (e.g the arm of a man and the front leg of a dog); analogous structures are structures that have similar functions in the absence of shared ancestry that have arose via convergence (e.g the wing of a bird and a butterfly). Vestigial structures, embryological similarities and biochemical and genetic tests provide additional evidence. 14.4 There is evidence that natural selection has and continues to operate Artificial selection refers to breeding by humans, field experiments on a variety of organisms document natural selection. 4 Chapter 16 16.1 Species are groups of populations that evolve independently. According to the biological species concept, a species is defined in terms of reproductive isolation (the ability of individuals in a population to successfully mate). While it is useful for many familiar species, it is not useful for asexually reproducing organisms or extinct groups. Similarity per se can be misleading. Organisms that look similar to one another might be distinct species; organisms that look quite different might nevertheless be part of the same species. 16.2 Isolating mechanisms prevent interbreeding Premating isolating mechanisms (geographic, ecological, temporal, behavior isolation and mechanical incompatibility) prevent mating from occurring at all. Postmating isolating mechanisms (genetic incompatibility, hybrid inviability and hybrid infertility) prevent production of fertile offspring after mating. 16.3 Speciation is the process by which new species form. It may occur by a variety of means, but invariably it involves a two step process: isolation of populations and genetic divergence (the build up of genetic differences between them) Allopatric speciation occurs when a geographic barrier of some sort prevents interbreeding; sympatric speciation occurs when genetic divergence occurs in the absence of a geographic barrier. Adaptive radiation may occur when many new species arise in a short period of time- usually when a species colonizes a new area with unoccupied habitats. 16.4 Extinction occurs as a result of a variety of different causes Localized distribution, overspecialization, interactions with other species, and habitat change. Chapter 17 17.1 Life on our planet began over four billion years ago. Historically many thought that new members of species might on a regular basis by means of spontaneous generation. This was disproven by Redi and later Pasteur and Tyndall. Modern scientific ideas on the subject begin with Oparin and Haldane, who drew attention to the fact that the early atmosphere of earth was quite different than it is now. Miller and Urey experimentally demonstrated that organic molecules could arise spontaneously in such an environment. Cech and Altman discovered a small RNA (ribonucleic acid) that can function as an enzyme (ribozyme). RNA was likely the first self-replicating molecule, the early earth might have been an RNA world of RNA molecules competing with one another There is also evidence that proteins and lipids shaken up to simulate the action of waves form vesicles. The first cell (protocell) might have consisted of a ribozyme enclosed by such a membrane. 5 17.2 The earliest organisms were anaerobic prokaryotes. They were unicellular, lived in the ocean and obtained energy by absorbing organic molecules in their environment. The evolution of photosynthesis about 3.5 billion years ago allowed some organisms to harness the energy of sunlight for the creation of complex, high energy molecules. This resulted in the release of large amounts of oxygen, a highly reactive molecule. The accumulation of oxygen in the atmosphere starting about 2.3 billion years ago led to massive extinctions of many anaerobic species and also the formation of the ozone layer, which protects life on earth from solar radiation. The dangers of oxygen led to the evolution of mechanisms to detoxify oxygen, and these mechanisms ultimately were coupled to reactions that form the basis of aerobic respiration According to the endosymbiont hypothesis, eukaryotes (cells with membrane bound organelles) arose by virtue of an anaerobic bacteria engulfing an aerobic bacteria. 17.3 The first multicellular organisms (algae) arose about 1.2 billion years ago. Multicellularity made them less vulnerable to predators, allowed individual cells to specialize. The first animals evolved 630 million years ago, resembled sponges and jellyfish. Predation amongst them favored the development of improved motility and senses, exoskeletons and later internal skeletons. 17.4 The first organisms to colonize land were plants, approximately 400 million years ago. Plants had to develop mechanisms to overcome the force of gravity in the absence of water to support them, the possibility of drying out, and also mechanisms to facilitate reproduction, including pollen, seeds, and later flowers and fruit. Arthropods were the first animals to colonize land, followed by lobefin fishes, the progenitors of modern amphibians, reptiles birds and mammals. 17.5 Mass extinctions have played a particularly important role in the evolution of live on our planet. The history of life on our planet can be seen in some ways as a series of succeeding dynasties. Mass extinction events have led one dynasty after another to fall, most of these have been the result of climate change. This includes changes due to plate tectonics, but also meteorites. 17.6 Humans evolved from primates (lemurs, monkeys and apes). Several key adaptations: binocular vision, grasping hands, a large brain, bipedal locomotion, made it possible for our hominoid ancestors to survive and thrive. Most branches of the hominid family have gone extinct. Modern humans emerged less than 200,000 years ago. 6 Biological and cultural evolution continues in humans to this day.
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