chapter 14 interactions in an ecosystem. animals and their habitats
TRANSCRIPT
Chapter 14
Interactions in an Ecosystem
Animals and Their Habitats
Biotic vs. Abiotic Factors
• An ecosystem is made of both biotic and abiotic factors.
• What biotic factors might scientists find in a Spectacled Bear’s habitat?
• What abiotic factors might be in a Spectacled Bear’s habitat?
• How do these factors differ for Polar Bears?
Habitat vs. Niche
• Habitat – describes the organism’s environment• Niche – describes how the organism interacts
with its environment– Includes both biological and physical conditions in
which an organism lives and how the organism uses those conditions for survival
– It can include its place in the food web, preferred temperature, and abiotic factors
– It is specific to each organism
Competitive Exclusion Principle
• This fundamental rule of Ecology states that no two species can occupy the same niche in the same habitat at the same time
• Why?
Symbiosis
• Symbiosis – any relationship where two species live in close contact
• Mutualism – both species benefit from the relationship
• Commensalism – one species benefits and the other is neither helped nor harmed
• Parasitism – one species harms the other
Mutualism, Commensalism or Parasitism?
How Populations Grow
• Important characteristics of populations: geographic distribution, density, growth rate
• Population density – number of individuals per unit area
• Population dispersion patterns: clumped, uniform and random
Survivorship Curves
• Survivorship curves are generalized diagrams showing the number of surviving members over time from a measured set of births.
• Type 1 – large mammals, low infant mortality, large number of elderly
• Type 2 – birds, small mammals, reptiles, equal survivorship rate through out ages
• Type 3 – fish, amphibians, plants, high mortality, high birth rates
Population Growth
• Populations fluctuate depending on different ecological pressures: births, deaths, immigration, emigration, etc.
• Immigration – individuals moving into an area• Emigration – individuals moving out of an area
Exponential Growth
• Occurs when the individuals in a population reproduce at a constant rate
• Typically occurs when a population has abundant space and food, and is protected from predators and disease
• Characterized as “unrestricted growth” meaning there are no external pressures placed on the population
• Will cease when carrying capacity is reached
Logistic Growth
• Begins as exponential growth• Population growth slows as a population
reaches its carrying capacity – the largest number of individuals an environment can support
• Birth rate may decline, death rate may increase, immigration or emigration may be fluctuating
Limits to Growth
• Limiting Factor – a factor that causes population growth to decrease
• Examples:
Density-dependent Limiting Factors
• These factors depend on population size• Competition – what happens when the
population increases, but resources stay the same?
• Predation – natural way of controlling population; predator-prey relationship is fluctuating
• Parasitism and Disease – may become more prevalent during high population density; limits population size similarly to predation
Density-independent Factors
• Affects all populations in similar ways, regardless of population size
• Examples:
Ecological Succession
• Ecosystems change in response to human as well as natural disturbances.
• What happens to an area after a forest fire? After a volcanic eruption?
• Primary succession – succession the occurs where no soil exists and usually begins with pioneer species
• Secondary succession – when change to the land occurs without removing the soil
Human Population Growth
• Human populations are affected by the same type of factors as other populations
• Because of technology, we have been able to increase our population size quickly
• Some say we have reached or even exceeded Earth’s carrying-capacity
• At the moment, we are still experiencing exponential growth
• Do you think we will experience logistic growth at some point?
Patterns of Population Growth
• Demography – the study of human populations• Scientists try to predict how human
populations will change over time based on birth rates, death rates and age structures
• Population growth has slowed in the US, Japan and Europe in the last 100 years
• Scientists refer to this as the demographic transition
Age Structure Diagrams
• Can be used to predict future population growth