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Chapter 5

Chapter 5. Populations and Communities. Standard 3. Standard 3: Students know and understand the characteristics and structure of living things, the processes of life, and how living things interact with each other and their environment. Vocabulary. Population Carrying capacity Predation

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Chapter 5

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  1. Chapter 5 Populations and Communities

  2. Standard 3 • Standard 3: Students know and understand the characteristics and structure of living things, the processes of life, and how living things interact with each other and their environment.

  3. Vocabulary • Population • Carrying capacity • Predation • Coevolution • Parasitism • Symbiosis • Mutualism • Commensalism • Niche • Fundamental niche • Realized niche • Competitive exclusion • Keystone species

  4. What is a population? • A population is a group of organisms of the same species that live in a specific geographical area and interbreed. • Population growth is important because populations of different species interact and affect one another, including human populations. • In the 1850’s two dozen rabbits were introduced from Europe. By the 1950’s there were 600,000,000 rabbits. What conditions were favorable for this huge growth?

  5. Population Growth (5:00) • Whether a population grows or shrinks depends on births, deaths, immigration and emigration. • Immigration is movement of individuals into a population. • Emigration is the movement of organisms out of a population. • Exponential growth occurs when numbers increase by a certain factor in each successive time period. This is indicated by a J-shaped curve.

  6. Carrying Capacity • Populations do not grow unchecked forever. Eventually due to food availability, predators and disease, the growth will slow and may stabilize. • The largest population that an environment can support at any given time is called the carrying capacity. • Density-independent factors are variables that affect a population regardless of population density, like fires, floods, weather. • Logistic growth is population growth that starts with a minimum number of individuals and reaches a maximum depending on the carrying capacity of the habitat.

  7. Factors That Affect Population Size • Abiotic factors are non-living factors that affect a population. Weather and climate are the most important. This includes water availability. • Biotic factors are living factors. Food, predators, and human activity affect populations. Common Abiotic Factors (6:35) Biotic Factors (3:57)

  8. Human Population • Today, human population is 6 billion and increasing. • Better sanitation, hygiene, disease control and technology have decreased the rate of death for human populations. What kind of graph is this, logistic or exponential?

  9. Interactions in Communities

  10. Parasitism • A parasite is an organism who is dependent upon a host. • Indian paintbrush (Castillejaindivisa) is a parasitic plant that obtains some of its nutrients and water from host plant--bluebonnet (Lupinustexensis). Indian paintbrush and bluebonnet

  11. Mutualism • Mutualism is a mutually beneficial relationship between organisms. • The bee feeds on the flower and pollinates it at the same time. Both benefit. • Coral Reef Ecosystem Bee and flower

  12. Commensalism • Commensalism occurs when one organism benefits from another without aiding or harming the host. • Remoras are “hitchhiker” fish that eat the leftovers of larger fish. They don’t help or hurt the fish, so it’s a commensal relationship. Whaleshark and remora

  13. Decomposers (0:54) When any organism dies, it is eventually eaten by detrivores (like vultures, worms and crabs) and broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues.

  14. Niche • A niche describes how an organism fits into an ecosystem. • Because each organism is unique, no two organisms can occupy the same niche in an ecosystem. Niches (1:33)

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