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YEAR 12 BIOLOGY. ECOLOGY. Overview. Organisms Components of an ecosystem Habitat Niche Adaptations Law of Tolerances. Overview. Populations Features Density and distribution Regulation Growth Patterns. Overview. Communities Food chain and webs Energy flow Nutrient cycles
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YEAR 12 BIOLOGY ECOLOGY
Overview • Organisms • Components of an ecosystem • Habitat • Niche • Adaptations • Law of Tolerances
Overview • Populations • Features • Density and distribution • Regulation • Growth • Patterns
Overview • Communities • Food chain and webs • Energy flow • Nutrient cycles • Species interactions • Competition
What is Ecology? • Ecology is a branch of science concerned with organisms, populations, communities and ecosystems. • Definition • The study of how organisms interact with each other and with their physical environment.
Species - Definition • Organisms belong to the same species if they normally interbreed and produce fertile offspring. • In some cases it is possible to classify organisms as belonging to the same species if they have similar characteristic.
Species - Subspecies • Considerable variety can exist between members of a species. • In some cases two or more quite distinct varieties exist. These different varieties are called Subspecies.
Subspecies • The Barssica’s
Classification Keys • Keys are used to identify organisms and to find the name of individual organisms. • TASK: • Using the “Life Science” textbook complete investigations 3 & 4.
Components of an Ecosystem • ENVIRONMENT • Both physical or non-living (abiotic) and biotic (living) factors affect the organisms in a community. These factors influence their distribution, survival, growth and reproduction. • Abiotic – the physical factors in an environment. These are non-living factors. • Biotic – the living factors within an environment.
Habitat and Niche • Habitat – The place or environment in which an organism lives is termed its habitat. It must not just include their general environment (e.g. forest, ocean) but include some detail about abiotic conditions in which these organisms must live in to survive.
Habitat and Niche • Niche – You could say that the habitat is an organism’s address, and that the ecological niche is its profession. The ecological niche is a description of; • the opportunities provided by the habitat; and • The adaptations of the organism that enable it to take advantage of those opportunities.
Habitat and Niche • The niche, then, is the role that the species plays in the community of interacting species. This includes; • Where it lives • What it eats • How it responds to stress, and • What limits its population growth • Biozone pg67-68
Ecological niche investigation • Collect a worksheet from the front of the class. • Using your instruction sheet, complete the investigation looking at the ecological niche of the ‘window’ and ‘notch’ caterpillar
Law of Tolerance Copy • An organism’s ability to survive variation in environmental conditions is called its Tolerance. • The law of tolerance states that: For each abiotic factor, an organism has a range of tolerances within which it can survive. Toward the upper and lower extremes of this tolerance range, that abiotic factor tends to limit the organism’s ability to survive.
Law of Tolerance • The wider the tolerance range of a species, the more widely dispersed the organism is likely to be. • Each species will have an optimum tolerance range within which the species will be most abundant. Outside of this optimum range, organism’s may experience physiological stress. • Biozone pg 65
Adaptations • These are inherited characteristics which enable an organism to survive and reproduce in a particular habitat. • Most organisms are a combination of many adaptations that allow them to fit into their environment easily. Adaptations are grouped into three types; • Structural • Behavioural • Physiological
Structural Adaptations • Physical structures of organisms which help ensure success in a habitat. • These include such things as; shape of the body, the colour, appendages. • Example: • Wide wings of birds that enable flight • Dense plumage of a Kea that provide insulation • Widely spaced eyes of a rabbit to increase field of vision to detect predators
Behavioural Adaptations • Ways in which members of a species act in order to increase their chance of survival. • These include such things as; defence behaviour, nocturnal or diurnal, hiding, spitting, stinging. • Example: • Bats roosting in colonies. Provides warmth and protection.
Physiological Adaptations • Processes that organisms carry out in order to survive. • Includes; anything to do with metabolism, the ability to tolerate high temps or more salty waters, secretion of enzymes for digestion, high reproductive rates • Example • Excellent hearing at high frequencies of bats to locate flying insects ( using echolocation clicks) • Biozone pg 70,74
Populations • Populations • Features • Density and distribution • Regulation • Growth • Patterns
Features of Populations • A population is a group of organisms which all belong to the same species and live in the same location • To define a population you need to know the type of individual, the time and the place e.g. all the buttercups on the sports field of our school in February, 2006.
Population Attributes • As an individual you are born, you grow and you die. A population has a birth rate and a death rate. • As there is normally a large number of individuals in a population, you can also measure population attributes. These include density, distribution, age structure, survivorship and life expectancy. • Biozone pg 76
Density & Distribution • Density – is the number of individuals of a population per unit area of habitat at a specific time. • In low density populations, individuals spaced will apart e.g. Tigers are solitary animals, found at low densities. • In high density populations, individuals are crowded together e.g. Termites form well organised, high density colonies.
Density & Distribution • Distribution – Populations tend to spread out in all directions until they come to a physical barrier. Within that barrier, they may be random, clumped or uniform.
Distribution patterns • a) random distribution • Spacing between individuals is irregular. • b) uniform distribution • Individuals are evenly spaced within an area • c) clumped distribution • Individuals are grouped in patches • Biozone pg 77 • Practical pg 126
Population Regulation • Population size is regulated by factors that limit population growth. • Density independent factors – regardless of population density, these factors are the same for all individuals. • Density dependent factors – the effects of these factors are influenced by population density. • Biozone pg 78
Population Growth • The number of individuals comprising a population may fluctuate considerably over time. Populations gain individuals through births or immigration and lose individuals through deaths and emigration. • Biozone pg 79 • A model – collect and complete the worksheet demonstrating growth of a sparrow population.
Population Growth Curves • Populations becoming established in a new area for the first time are often termed Colonising populations. • These show an exponential growth curve. • If the resources in the new area were endless then the population would continue to increase at an exponential rate.
Population Growth Curves • However, in a natural population, initially the growth may be exponential but as the population grows, its increases will slow and it will stabilise at a level that can be supported by the environment. • This is called the CarryingCapacity or K. • In an established population the population numbers will fluctuate about K. • Biozone page 81
r and k Selection • There are two parameters that govern population growth • r and k selection • r selection refers to the maximum reproductive potential of an organism and r-selected species are those with a high intrinsic capacity for population increase. • k refers to the carrying capacity of the environment and k-selected species exist near this point of equilibrium with the environment
r and k-selection • R-selected species tend to be opportunists because they are poor competitors and must continually invade new areas in order to gain the advantage of their high reproductive potential. • K-selected species are also called competitor species because they are challenged in competitive environments to use available resources more efficiently and thereby compensate for their lower reproductive potential.
Life Tables and Survivorship • Data collected during a population study can be presented as a table called a life table or graphically as a survivorship curve. • The shape of a survivorship curve shows graphically at which life stages the highest mortality occurs.
Survivorship • There are three types of survivorship curves • Type I • Mortality is very low in the infant and juvenile years, and throughout most of adult life. Mortality increases rapidly in old age. • Type II • Mortality is relatively constant through all life stages (no one age is more susceptible than another) • Type III • Mortality is very high during early life stages, followed by a very low death rate for the few individuals reaching adulthood.
Population Age Structure • The age structure of a population refers to the relative proportion of individuals in each age group in the population. • The population is usually divided into three groups • Pre-reproductive • Reproductive • Post-reproductive
Population Age Structure • This is usually shown as a age pyramid. The shape of the pyramid show different things • True pyramid – an expanding population • Bell shaped – a stable population • Urn shaped – a diminishing population
Patterns in Ecology • The three patterns we will be looking at are: • Succession – the change in species over time • Stratification – the vertical layering of organisms • Zonation – the horizontal bands of organisms which form in relation to a gradient in a major environmental factor.
Ecological Succession • After a disaster, new organisms colonise the land, and each modifies the environment so that is becomes suitable for a new species. • This change in species composition over time is called ecological succession.
Ecological Succession • The community passes through a sequence of stages (seres) until eventually a stable climax community is formed.
Primary Succession • Primary succession refers to the colonisation of regions where there is no preexisting community. • Examples include • New volcanic islands • New coral atolls • Islands with communities that have been extinguished by a volcanic eruption.
Secondary Succession • This occurs when an existing community has been cleared by some disturbance that leaves the soil intact. • In this case the area often eventually returns to its original state. • Secondary succession can be broken down into two types: Catastrophe cycle and Gap regeneration.
