eCOLOGY 2.docx

Competition Competition is the struggle between organisms for the same resource e.g., grass, dandelion, buttercup, and daisy compete for space, light, water, minerals; fox, thrush and hedgehog compete for earthworms. Competition reduces population numbers. Intra-specific competition takes place betw...

Competition Competition is the struggle between organisms for the same resource e.g., grass, dandelion, buttercup, and daisy compete for space, light, water, minerals; fox, thrush and hedgehog compete for earthworms. Competition reduces population numbers. Intra-specific competition takes place between members of the same species. Inter-specific competition involves different species e.g., blackbirds and thrushes competing for snails and insects. The two types of competition are: - Contest competition is an active physical confrontation between two organisms which allows one to win the resource e.g. competing stags (red deer) interlock anthers until one withdraws when competing for a mate. Robins – birdsong in spring is male robins warning off others from their territory. - Scramble competition each organism tries to acquire as much of the resource as possible e.g., chicks in nest depending on parent for food. Effects of competition - brings about evolution of a better-adapted species and elimination of the less well-adapted species. Adaptations to survive competition - A grass plant produces large quantities of pollen increasing its chance or reproduction. - Blackbird ‘song’ is to warn competitors to stay away. - Yellow petals of buttercups to attract insect pollinators. - Bacteria in soil secrete chemicals to inhibit their competitors. - The caterpillar of the cabbage white butterfly chews on cabbage leaves, while the adult butterfly drinks nectar from flowers. - Creeping buttercup uses fast-growing horizontal stems to colonise the habitat faster than dandelions. Predation Predation is the catching, killing, and eating of prey by its predator. Predator: an animal which kills other animals to use as a source of food. Prey: an animal that is caught and killed for food. Prey Predator Insects Spiders Fish/birds Humans Aphids Ladybird Predator adaptations **Know Three** - A fox has a. reddish fur used for camouflage to avoid detection by rabbits. b. Long canine teeth to kill prey and tear flesh. c. Great speed to outrun prey to capture it. Factors that improve the efficiency of predators: - Keen eyesight (e.g. hawk and other birds of prey), hearing, sense of smell and dentition - Catching whatever is easy, prevents wasting energy. - Being able to change diet as numbers of prey change e.g. foxes and spiders. - Living in packs can help locate food and make prey easier to catch. - Being able to migrate to areas where the prey is more plentiful - Camouflage - Catch large, rather than many small prey. - Ladybirds have strong mouthparts to enable them to chew aphids. Prey adaptations **Know Three** -Features that assist Rabbits to avoid being eaten: a. Rabbit digs narrow underground burrows – large predators are too big to enter. b. long ears – good hearing to detect predator. c. White tail – conspicuous warning signal to other rabbits. - Plant adaptations a. Some have thorns, spines, and stings e.g., holly and cacti. b. Some plants have a nasty taste to deter predators e.g., giant hogweed. - Animal adaptations a. Some can swim, fly and run faster than predator. b. Mimicking animals the predator would normally avoid e.g. hoverfly is a harmless insect but protects itself by mimicking the colouration of wasps. c. Staying in large groups e.g. in flocks and herds like deer. d. Camouflage enables them to blend with surroundings e.g. greenfly, stick insects, frogs. e. Warning colouration as seen in many butterflies and moths e.g. the spots on the wings of the peacock butterfly appear as eyes. f. Poisons e.g. caterpillar of large white butterfly, ladybirds contain large amounts of formic acid, which is unpalatable to predators. g. Mice flee and hide to avoid being eaten. Effects of predation in ecosystem: Predation maintains the prey species at a sustainable level. Predation is a major factor in evolution of the prey species. - Predation initially increases the numbers of predators and decrease the number of prey. - The numbers of predators and prey often show repeated cycles of rising and falling numbers. Predator-Prey Relationship **Need to Know** This is used in the biological control of pests. For example, ladybirds are used to control greenfly. Certain bacteria are used to control the larvae of butterflies to prevent them from destroying crops like cabbage. Parasitism Parasitism occurs when two organisms of different species live in close association and one organism (parasite) obtains its food from, and to the disadvantage of, the second organism (host). Parasite is an organism that feeds from and harms another organism. - Endoparasites: feed in a living host e.g., liver fluke, potato blight fungus, bacteria of disease in human body. - Ectoparasites: feed on the outside of the host e.g., fleas, athletes foot fungus, mosquitoes on human skin, greenfly on a rosebush, blood-sucking leeches on human skin, lice on hawks Parasites are often thought of as predators, but they differ by: a. Being smaller, often attacking from within b. being dependent on one particular host c. only do a small amount of damage to host so that they do not harm their food source or home. Parasites sometimes reduce the numbers in a population e.g., potato blight or disease-causing bacteria, but often have little effect on host numbers. Symbiosis Symbiosis is a close relationship between two organisms of different species in which at least one of them benefits. Symbiosis increases the numbers of both species In one type of Symbiosis, mutualism, both organisms’ benefit. Examples of this are - Lichen: it consists of a fungus and an alga. The alga makes food for both, and the fungus absorbs minerals and water for both and give protection and support. - Nitrogen–fixing bacteria: in root nodules of legumes e.g., clover. Bacteria provide nitrates for plants to make protein and plants provides carbohydrates, shelter and anaerobic conditions for bacteria. - Bacteria: living in large intestine, supply us with vitamins B and K and protect us from pathogenic bacteria. We supply bacteria with food, water, and a protected site to live. Population Dynamics Population dynamics refers to the factors that cause changes in population numbers. Predator-prey numbers interact due to: a. availability of food: increases predator numbers when high but reduces them when low b. concealment: which means that some prey survive by hiding from the predators c. movement of predators: which means that predators move to new areas when prey numbers are low. (9) Human Population **Need to Know Examples** Human population continues to rise despite famine, disease, war, and contraception. The sudden increase in the twentieth century was due to fewer infant deaths and people living longer because of improved sanitation and medicines and disease eradication programmes. Numerous factors affect human population, including; - Famine: occurs when an acute shortage of food affects a population. Famine can lead to starvation, death, and mass emigration. Famine is often linked to war as war zones have reduced agriculture. -Disease: The ability to control and cure diseases (vaccines, antibiotics, improved sanitation, insecticides, safe anaesthetics, improved surgical methods and new drugs) have helped to reduce the death rate and increase human numbers. - Wars: War normally reduces population numbers temporarily due to death. Baby booms often follow wars. - Contraception: The use of contraceptives has reduced the birth rate.