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This chapter explores essential concepts of populations, including size, density, and dispersion, examining how these factors fluctuate over time due to various influences like birth, death, emigration, and immigration. It delves into the idea of carrying capacity—the maximum population size supported by the environment—alongside the dynamics of population regulation through density-dependent and independent factors. The chapter also covers species interactions, such as predation, competition, and symbiosis, detailing their implications for survival and community dynamics, along with the processes of ecological succession.
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Chapter 19-20 Populations and Species Interactions
Properties of a Population • Population – a group of organisms that belong to the same species and live in a particular place at the same time. • Population size – the number of individuals that the population contains. • Size is fundamental and important to population • Population Density – measures how crowded a population is. • Human population density in America is 30 people per square kilometer. • Dispersion – spatial (3D) of individuals within a population • Clumped – individuals are clustered together • Uniform – separated by fairly consistent distance • Random – independent of others location
Population Dynamics • Populations change over time. There are many different reasons or things to consider when looking at the change. • Birth rate • Death rate • Life Expectancy
Population Growth Rate • Growth rate – the amount by which a population’s size changes in a given time. • The growth rate depends on: • Birth • Death • Emigration – movement of individuals out of the population • Immigration – movement of individuals into a population • Growth rate can be found by: Birth rate – death rate = growth rate
Carrying Capacity • It is the number of individuals the environment can support over a long period of time.
Population Regulation • Density – independent factors – reduce the population by the same proportion, regardless of the population’s size. • Floods, fire, weather • Density – dependent factors – an individual’s chance of surviving or reproducing depends on the number of individuals in the same area • Resource limitations: food shortage, nesting
Species Interaction • Predation – an individual of one species, called the predator, eats all or part of an individual of another species call the prey. • Species adapt in order to avoid being prey. • EX: venom, heat sensitive pits, sense of smell = snake • EX: sticky webs of spiders • EX: Amazonian poison frog uses its bright skin to warn everyone it is poisonous • Mimicry – one species closely resembles another species
Competition • Interspecific competition – type of interaction in which two or more species use the same limited resource. • EX: plants competing for sunlight • EX: Lions and hyenas compete for zebra’s as food • Competitive Exclusion – situation where on species is eliminated from a community because of competition • Reduced niche size – can cause inter species competition
Symbiosis • Symbiosis – close, long-term relationship between two organisms. • Three types: • Parasitism – one individual is harmed, one benefits • Mutualism – both benefit • Commensalism - one individual benefits, one is unaffected
Succession • Primary Succession – development of a community in an area that has no life forms • Pioneer species – 1st to in habit the area • Secondary Succession – development of a community in an area that has been damaged, but still has life form
