SOL LS.8 Ecosystems, communities, populations change over time      click for printable version

ORGANISMS RESPOND TO DAILY, SEASONAL, AND LONG-TERM CHANGES CHANGES IN THE ENVIRONMENT MAY INCREASE OR DECREASE POPULATION SIZE LARGE-SCALE CHANGES SUCH AS EUTROPHICATION, CLIMATE CHANGES, AND CATASTROPHIC DISTURBANCES AFFECT ECOSYSTEMS Organisms respond to Daily, Seasonal, and Long-term changes To survive, plants require light and water for photosynthesis. Plants have developed responses, called tropisms, to help ensure they grow toward adequate sources of light and water (i.e., phototropism and geotropism). Some plants and animals can better survive adverse environmental conditions through periods of dormancy. Dormancy occurs when normal physical functions are slowed down or suspended. A circadian rhythm is a roughly 24-hour cycle in the physiological processes of living things, including plants, animals, fungi, and cyanobacteria. This cycle aids life processes Population size responds to changes in the environment  Systems are dynamic and change in response to inputs and outflows of energy and matter. Factors can positively and negatively affect the cycles of matter and the life processes of living things within an ecosystem.  Disruptions to any component of an ecosystem can lead to shifts in the size and/or distribution of its populations . Changes in the living and nonliving components of an ecosystem can accelerate or decelerate natural processes. Many factors such as pollution, habitat destruction, disease, and over-harvesting can increase or decrease population size. Eutrophication, Climate changes, and Catasrophic disturbances affect Ecosystems Systems are comprised of a group of interacting and interdependent elements forming a complex whole. Systems change in response to inputs and outflows of energy and matter. A change in one part of the system affects other parts of the system.  Long-term changes may affect entire communities and ecosystems. When excess nutrients flow into an aquatic ecosystem, a chain of events may take place which leads to a low dissolved-oxygen level in the water. This is called eutrophication.  Natural disasters, such as forest fires, floods, and tornados are disruptive factors that shift the balance with in an ecosystem and initiate a process of gradual change from one community of organisms to another. You should be able to: categorize responses as daily, seasonal, or long-term and explain the benefits of particular responses to long-term survival. predict the effect of long-term, short-term, or seasonal changes on the size and distribution of populations in an ecosystem compare the factors that increase or decrease population size predict the environmental effects of large-scale changes, such as climate change, ocean acidification, and sea-level rise

SOL LS.9 Human activity and ecosystems

CHANGES IN HABITAT CAN DISTURB POPULATIONS DISRUPTIONS IN ECOSYSTEMS CAN CHANGE SPECIES COMPETITION VARIATIONS IN BIOTIC AND ABIOTIC FACTORS CAN CHANGE ECOSYSTEMS Changes in habitat can disturb populations Changes in the interactions among the living and nonliving components of an ecosystem cause change in the system. Factors (natural and human-caused) can positively and negatively affect the cycles of matter and the life processes of living things within an ecosystem. Humans are a natural part of the ecosystem. Humans use the ecosystem to meet their basic needs, such as to obtain food . Disruptions in ecosystems can change species competition Human input can disturb the balance of populations in a habitat. These disturbances may lead to a decrease or increase in a population's size. Since populations in an ecosystem are interdependent, these disturbances can have a ripple effect throughout the larger ecosystem. Variations in biotic and abiotic factors can change ecosystems The interaction of humans with the dynamic ecosystem may lead to changes in climate, water supply, air quality, energy production, ocean acidification, and waste management . You should be able to: describe ways that human interaction has altered habitats positively and negatively. describe the relationship between human food harvest and habitat stability. debate the pros and cons of human land use vs. ecosystem stability. compare population disturbances that affect competition among species and species survival. use evidence to describe the impact of human activity on the biotic and abiotic factors within an ecosystem.