Introduction to Ecosystem Homeostasis (OCR)

UNIT 1: INTRODUCTION THE BIOLOGICAL WORLD: Balance in Natural Communities Ecosystem Homeostasis UNIT 1: INTRODUCTION  property of living organisms in which internal systems are kept in balance or maintain stable internal conditions UNIT 1: INTRODUCTION What could happen i...

UNIT 1: INTRODUCTION THE BIOLOGICAL WORLD: Balance in Natural Communities Ecosystem Homeostasis UNIT 1: INTRODUCTION  property of living organisms in which internal systems are kept in balance or maintain stable internal conditions UNIT 1: INTRODUCTION What could happen if the body did not maintain homeostasis for an extended period?  homeostatic balance is disrupted (homeostatic imbalance)  lead to a state of disease  cellular malfunction LIFE’S HEIRARCHY OF LEVELS An ecosystem regulates itself. Homeostasis is the dynamic equilibrium among the living members of an ecosystem, and with their ever-changing environmental conditions, such as wind, rainfall, nutrient availability, air quality, and climate.  A self-regulating process by which biological systems tend to maintain stability while adjusting to conditions that are optimal for survival.  If homeostasis is successful, life continues; if unsuccessful, disaster or death ensues.  The stability attained is actually a dynamic equilibrium, in which continuous change occurs yet relatively uniform conditions prevail Homeostasis mechanisms chiefly concern: 1. Matters cycling and energy flow 2. Protection of production level 3. System structure Mechanisms to attain equilibrium in nature  1. Attack-Avoidance as Homeostasis  Inmammals and birds, especially, members of the same species spend a lot of time and energy harassing each other, chasing each other, fighting (but not hurting each other much), and avoiding each other. This is called Attack-Avoidance behavior. 2. Overcrowding Homeostasis  In many species, especially in small consumers such as mice, rabbits and lemmings, over-crowding creates an increasing stress that damages the thyroid gland, which manufactures essential hormones.  When population densities reach a critical point, the stress becomes extreme and much of the population simply drops dead from endocrine (hormone) system damage. 3. Prey Abundance and Homeostasis  When the prey of predators is super- abundant, the predator will have more young. So the predators become as super- abundant as prey.  Ifa niche opens in an ecosystem, life fills it as quickly as possible. The prey population crashes. The predators have little choice. They can travel, or starve. 4. Homeostasis in Reproduction (multiple birth)  Another homeostatic process which regulates population is multiple births. In some species, such as deer, crowding results in single births. When the same species is not crowded, twins are the rule.  Populations adjust themselves to "undercrowding" and “overcrowding”. If there is a niche (a way to make a living) available in an ecosystem, life will fill it. BIODIVERSITY vs. MONOCULTURE Biodiversity  In any living community, the more different kinds of organisms there are, the stronger that community will be.  In other words, The more variety of life- forms in an ecosystem, or the more differences there are among the inhabitants, the healthier the community will be, and the more adaptable and resilient the community will be. Monoculture  Monoculture-a managed refusal of diversity.  Monoculture - the practice of growing single crops on a piece of land, often for year after year. Usually that crop is one bred variety of one species Results of monoculture:  heavy use of chemical fertilizers  heavy use of chemical poisons (herbicides, insecticides)  increased susceptibility to diseases  low tolerance to stresses of drought or temperature  reduced resistance to insects Results of monoculture:  crop failures resulting in famines  reduced soil fertility  increased soil erosion  permanent loss of genetic variety in the crop species  increased habitat for “pest” species  reduced habitat for beneficial species BIOLOGICAL CONTROL OF PLANT PATHOGENS Introduction Plant diseases need to be controlled to maintain the quality and abundance of food, feed, and fiber produced by growers around the world. Different approaches may be used to prevent, mitigate or control plant diseases.  Beyond good agronomic and horticultural practices, growers often rely heavily on chemical fertilizers and pesticides. Such inputs to agriculture have contributed significantly to the spectacular improvements in crop productivity and quality over  The environmental pollution caused by excessive use and misuse of agrochemicals has led to considerable changes in people’s attitudes towards the use of pesticides in agriculture  Today, there are strict regulations on chemical pesticide use, and there is political pressure to remove the most hazardous chemicals from the market In Natural Ecosystem Pests co-exist in a complex relationship with plant communities They are associated with a number of activities, both harmful and beneficial Under natural condition, they interact with each other creating a balance – prevent excessive population of one species over the other. Effect of growing crops When the natural ecosystem is disturbed due to growing a particular crop, there is also a corresponding effect on the relationships of pests in nature Leads to the disturbance of balance between the hosts and pest communities Effect of growing crops ex: The use of inorganic pesticides in production areas lead to a shift in the population of pests and development of strains/species which are more resistant to the chemicals applied. The use of broad spectrum pesticides also kills the beneficial groups present in the area. Harmful effects of pesticides: pest resistance pest resurgence harm non-target organisms increase pesticide residues on crops and bodies of animals pollute the environment  Experts from John Hopkins Bloomberg School of Public Health (2002) says that: “ The world uses 3 million tons of pesticides yearly.”  Such inputs to agriculture have contributed significantly to the spectacular improvements in crop productivity and quality over the past 100 years.  Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species, including non-target species, air, water, bottom sediments, and food Have you eaten your poison today?  Studies showing negative effects of synthetic pesticides on humans and the environment have been reported.  Manalo (2012) of the PhilRice Magazine reported that over 160 pesticides are classified as carcinogenic  beneficial organisms are the first INTEGRATED PEST MANAGEMENT (IPM) An ecological approach of controlling pests which utilizes a combination of several strategies or tactics like plant resistance, cultural, biological and chemical control.  strategy that started in the 70’s  aimed to efficiently manage pests  PaulTeng of IRRI: IPM adoption in Asian countries resulted in “large savings from reduced importation of pesticides with no reduction in total rice output or productivity.” BIOLOGICAL CONTROL In Entomology, it has been used to describe the use of live predatory insects, entomopathogenic nematodes, or microbial pathogens to suppress populations of different pest insects. BIOLOGICAL CONTROL In Plant Pathology, the term applies to the use of microbial antagonists to suppress diseases as well as the use of host-specific pathogens to control weed populations. In both fields, the organism that suppresses the pest or pathogen is referred to as the biological control agent (BCA). More broadly, the term biological control also has been applied to the use of the natural products extracted or fermented from Biological Control natural products More narrowly, biological control refers to the purposeful utilization of introduced or resident living organisms, other than disease resistant host plants, to suppress the activities and populations of one or more plant pathogens. Types of interactions contributing to biological control Throughout their life cycle, plants and pathogens interact with a wide variety of organisms. These interactions can significantly affect plant health  In order to understand the mechanisms of biological control, it is helpful to appreciate the different ways that organisms interact.