Population Dynamics PDF

K. Winson & M. Pather 2020 REVISED ATP 2021  WHAT IS IT? The study of the factors influencing the population size, growth rate, growth forms and distribution of individuals in a population One organism of a population of a particular species A group of individuals of a particula...

K. Winson & M. Pather 2020 REVISED ATP 2021  WHAT IS IT? The study of the factors influencing the population size, growth rate, growth forms and distribution of individuals in a population One organism of a population of a particular species A group of individuals of a particular species Multiple populations of different species in the same area Community of living organisms and the non-living factors around them A group of similar ecosystems All the ecosystem s on Earth One Grade 11 pupil - individual All Grade 11 pupils at Newton House- population Grade 11s (humans) + rats + cats+ ants + trees + grass + flies + fish = community The community + all non-living factors (soil, air, water, sunlight) at Newton = ecosystem In the Grassland of Gauteng = biome SO WHAT IS THE DIFFERENCE..? Species: Group of organisms with similar characteristics who are able to interbreed and produce fertile offspring Population: A group of organisms of the same species living in the same area who are able to interbreed Community: A number of different populations living in the same area Ecosystem: Groups of different species interacting with each other as well as the non-living factors in that particular area Environment: The biotic and abiotic factors surrounding an organism and influencing its development and survival  Lions in Mosquitos in Humans in Kruger Park the Bahamas Gauteng Palm trees in Hawaii Elephants in Sharks in the Kenya Tigers in Atlantic India Ocean Ants in Polar bears in Newton the North These are all examples of House Pole populations Chickens in Tulips in Oak trees in the world Holland England  CHARACTERISTICS OF A POPULATION Populations have characteristics that apply to the group as a whole. Examples of these characteristics are: 1. Density – Number of individuals per unit area eg. (how many Grade 11 pupils per 100m² at Newton House) 2. Sex ratios – Ratio of the number of male to females in the population 3. Pattern of distribution – Refers to how the individuals of a population are distributed over the area they occupy (where in the school are the Grade 11s)  WHAT CAN HAPPEN TO THE POPULATION SIZE? The size of a population can increase, decrease or stay stable. Certain factors (parameters) will cause the size of a population to change.  POPULATION PARAMETERS Natality Mortality Increase Decrease the size of the size of a a population population Immigration Emigratio n  POPULATION SIZE NATALITY: Birth rate of a population MORTALITY: Death rate of a population IMMIGRATION: One way movement of organisms into an area EMIGRATION: One way movement of organisms out of an area MOVEMENT OF A POPULATION Immigratio Emigration Migration n One way One way Two way Periodic movement from Out of an one location to Into an area area another, in response to change of season EFFECT OF THESE PARAMETERS NATALITY and IMMIGRATION exceed Populatio mortality and n will emigration GROW EFFECT OF THESE PARAMETERS MORTALITY and Populatio n will EMIGRATION DECLINE exceed natality and immigration EFFECT OF THESE PARAMETERS When Population will parameters are be stable roughly equal Natality Mortality Immigratio Emigration n EFFECT OF THESE PARAMETERS CLOSED POPULATION: A population in which immigration and emigration do not occur eg. fish in a dam or animals on an island  LIMITING FACTORS Factors that help to regulate the growth of a population are known as limiting factors. These limiting factors may be: DENSITY DENSITY DEPENDENT INDEPENDENT Factors which have a Factors that regulate greater effect when the population size the population regardless of the size density is high of the population eg. competition, eg. Natural disasters, predation, disease, unusual weather famine patterns, drought, floods  LIMITING FACTORS - Certain factors that prevent unlimited growth in a population are known as limiting factors. - Together, these factors are known as environmental resistance - Examples of limiting factors are: - Shortage of food and water - Shortage of living space - Shortage of shelter - Diseases and parasitism - predation  SO HOW DO POPULATIONS GROW? Bacteria Humans Palm trees Lions Frogs Pigeons Ants Roses Zebra Not all species will grow in the same way, at the same speed  Population Growth Pattern on increase in a population is known as growth form. 1) Geometric or Exponential Growth: - Growth of the population is unlimited - J – shaped  Population Growth 2) Logistic Growth: Growth is gradual, rapid and the slows down again S- shape GROWTH CURVES  Population Growth Forms - Geometric Population grows very rapidly. No limiting factors to hinder population Growth growth. phase Lag phase Little/no growth due to population becoming accustomed to new environment J- shaped  GEOMETRIC (J-SHAPED) GROWTH - A population can reach its full reproductive potential when it has unlimited resources such as food, water, space and no predators - These ideal conditions result in the maximum possible growth rate and the population increases rapidly  GEOMETRIC (J-SHAPED) GROWTH - Initially the increase in numbers is slow, as there are few individuals - In time, there is a sharp increase in individuals and the graph rises steeply Population Growth Forms - Logistic S - shaped  A dotted line on a population growth curve, such as the one above, is known as the CARRYING CAPACITY. This is defined as the MAXIMUM number of individuals that a specific environment can sustain LOGISTIC (S-SHAPED) GROWTH - This kind of growth form occurs when a young population, of only a few individuals, is located in an area with sufficient food, water, space and little predation - There are 4 distinct phases: 1. Lag/ establishment phase 2. Accelerating growth phase 3. Decelerating growth phase 4. Equilibrium/stationary phase -  LAG PHASE Population grows sloooooooowly Why???? - Organisms are acclimatising to their environment - Becoming sexually mature - Looking for partners  ACCELERATING GROWTH PHASE Population grows rapidly!!!!!!!!! Why??? - Very little or no environmental resistance (ie. enough food, water, shelter etc) - Birth rate higher than death rate DECELERATING GROWTH PHASE Population grows, but not as rapidly Why??? - Birth rate still higher than death rate, but environmental resistance increases - Available resources start to decrease, so competition for food, water, shelter, mates etc increases  EQULIBRIUM PHASE The population numbers stabilise Why??? - Natality and mortality are approximately equal - Population reaches the carrying capacity and stabilizes around this number  REGULATION OF POPULATION SIZE Once a population reaches its maximum size in a given environment, the numbers will not remain constant, but fluctuate within narrow boundaries due to changes in environmental resistance. A STABLE population is a population where the numbers fluctuate around the carrying capacity  A stable population  SURVIVORSHIP CURVES A survivorship curve is a graph showing the number of individuals surviving to each age for a given species or group (e.g. males or females).  Many individuals survive to an old age Few individuals survive to old age  INTERACTIONS IN THE ENVIRONMENT Organisms in an environment are constantly interacting with each other. Five types of interaction occur: - Predation - Competition - Mutualism - Commensalism - Parasitism  SYMBIOSIS A close association between two organisms Parasiti Mutualis Commensal sm m ism Relationship Relationship between two Relationship between two organisms of between two organisms of different organisms of different species in different species such which one species where that one benefits from both benefit organism the association without benefits and the and the other harming one other neither (the host) is another. benefits nor is harmed harmed  PARASITISM Tapewor m Plasmodium parasite (Malaria)  MUTUALISM Nitrogen-fixing bacteria (N-gas to NO³) in nodules on legume Lichen – algae & plants (clover/soybean)fungus live together. Fungus extracts minerals from tree and algae uses it for photosynthesis. Fungus obtains carbohydrates from algae. Hermit crabs occupy empty mollusc shells to protect their soft bodies. Sea anemone attached to empty mollusc shell. Sea anemone (stinging cells) protects hermit crab from predators. COMMENSALISM Shark and remora fish – remora fish feeds on scraps of shark’s food. Remora fish benefits, shark neither benefits nor is harmed. Barnacles on a whale – Whale is not harmed neither does it benefit. Barnacles benefit by moving to fresh food supply in the ocean. Commensalism - Barnacles on whales PREDATOR PREY RELATIONSHIP PREDATOR: Organism that hunts and kills another organism for food PREY: Organism that gets hunted and killed by another organism for food  PREDATOR PREY RELATIONSHIP The higher the number of prey, the more predation occurs Lower the number of prey, the fewer predators will survive because of a lack of food  PREDATOR PREY RELATIONSHIP 1. As prey numbers increase, there is a corresponding increase in predator numbers as more food is available 2. Therefore more predation occurs 3. The prey numbers decrease 4. As the food source decreases, the predator numbers also begin to decrease 5. A decrease in predator numbers leads to an increase in prey (they are not being caught and eaten) 6. The cycle will be repeated COMPETITION – two or more individuals competing for the same limited resource Examples of INTERSPECIFI INTRASPECIFI resources – C C food, water, shelter, COMPETITION COMPETITION space, mating partners Between Between organisms of organisms of DIFFERENT the SAME species species  INTRASPECIFIC COMPETITION Between organisms of the SAME species E.g. Male antelope fighting for territory, male Sometimes the competing Lions fighting or suckling kittens individuals are forced to share the available resources Sometimes one individual ‘wins’ the resource and the other dies or leaves. Territoriality : the process that occurs when animals patrol or mark an area and defend it against members of their own species This is how many animals compete for space and food. Birds- patrol boundaries, songs Dogs/cats/rhinos – urine/dung Antelope- gland on head to  INTERSPECIFIC COMPETITION Competition between individuals of different species They do not compete for ALL the same resources  competition not as intense as intraspecific When two species with similar niches occupy the same habitat  niches overlap = 2 possible outcomes 1) Competitive exclusion 2) Competitive coexistence Ecological niche – functional role and position of a species within an ecosystem. How and when resources are used How it interacts with other species & physical environment **Greater similarity between niches of 2 organism = greater competition**  COMPETITION eg. COMPETITIVE EXCLUSION - Between two DIFFERENT species - One species will outcompete the other, resulting in the other species leaving the area (emigrating) or possibly even becoming extinct COMPETITIVE EXCLUSION E.g. Vervet monkeys and Lemurs -Lemurs were found all over Africa -Monkeys evolved -Occupied same ecological niche (same food, space ,trees)  increased competition  monkey more successful -Lemurs became extinct  only found in Madagascar (no Vervet monkeys)  COMPETITION e.g. COMPETITIVE CO-EXISTING - Between different, but similar, species - Use limited resources at different times, in different ways or in different places - Therefore, the species can co- exist  RESOURCE PARTITIONING Two competing species coexist in the same ecosystem Overlapping niches  compete for the same resources but able to coexist as they use resources differently (Resource partitioning) 2 types of resource partitioning a) Temporal partitioning: when two species use the same resources but at different times. b) Spatial partitioning: when two species use the same resource but they use different Giraffe parts of and it orKudu they use the same resource but in different places.n Birds of costal wetlands Owls and hawks  Human Population Factors previously discussed can apply to human population numbers Humans with their intelligence have been able to manipulate and change their environment to suit their needs e.g. planting more crops when running out of food The environment will only stand so much intervention by people with unlimited population growth This will have negative effects on the environment such as climate change, pollution and extinction of some species HUMAN POPULATION GROWTH CURVE  DETERMINATION OF HUMAN HUMAN POPULATION SIZE POPULATION SIZE (1650 TO PRESENT) ESTIMATION OF HUMAN Population POPULATION SIZE UP TO 1650 increasing continually radiocarbon dating – pg 86 (fossils/weapons) rate of no. weapons/tools = est. population size population distribution of growth is archaeological increasing sites = population distribution doubling Population rose from 5 period million, ten thousand yrs becoming ago shorter (8000 BCE) to 200/300 million (O CE) UNDERSTANDING HUMAN POPULATION GROWTH PERIOD POPULATION CHARACTERISTICS Prior to 1650 Moved from place to place, taking what is required to HUNTER- satisfy needs. When they moved, original habitat had a GATHERERS chance to recover. 1650 Chose a suitable habitat and settled there. Environment AGRICULTURAL became degraded – constant demand for resources. More REVOLUTION efficient farming, more food available. Population increased. 1750 Agricultural efficiency increased. Provision for housing INDUSTRIAL increased. More people derived income thus larger REVOLUTION families. Birth rate increased. 1800 Technological advancements, improvement in sanitation, MEDICAL decrease in disease. Increase in medical technology – REVOLUTION control of infectious diseases, death rate reduction.  1850 Development of larger cities, densely populated. Land LARGE CITY cleared to create space for housing. Exploitation of DEVELOPMENT resources to satisfy needs of large population. Further degradation of environment – erosion, deforestation, global warming. POPULATION GROWTH IN DEVELOPED & DEVELOPING COUNTRIES  Census figures = how many AGE PYRAMIDS people of each age group are present in a population Used to plot an age pyramid for population Age pyramid = no. of individuals in each age group Pyramids useful in predicting whether population will increase, decrease or remain Size of each box stable represents the number Useful in planning for : of individuals of that schools, housing, age employment, social welfare, medical services, INCREASING POPULATION Base of pyramid – wide Narrows towards top Many individuals in younger age group Population increases in size High death rate with increasing age eg. Kenya, Nigeria, Brazil, SA STABLE POPULATION Stable population Similar population size at each age group Birth and death rate almost the same. Population remains +- the same. eg. Europe, USA DECREASING POPULATION Declining population Pre-reproductive age group less than reproductive /post- reproductive age As older individuals die, less youngsters to replace them – declining population. eg. Germany, Russia  ECOLOGICAL FOOTPRINT Refers to the area of land people require to support their lifestyle Simple lifestyle = Demanding LIGHT lifestyle = HEAVY FOOTPRINT FOOTPRINT Small/ moderate High degree of impact on environmental environment degradation  ESTIMATION OF POPULATION SIZE FOR THE How is this done? Studying present FUTURE population growth trends & calculation of current growth rate Extend trend into future to project population figures for future. Present rate of increase = 1.6%/ annum indicates: > 7000 mill people by 2010 +- 8000 mill by 7.7 billion as of September 2019 2019