Starter Questions

Starter Questions • Write down the 5 freedoms for animal welfare • Why are animals/animal products from the UK more expensive? • What is stereotypy? • Give an example of stereotypy • What is misdirected behaviour? • Give an example of misdirected behaviour

Higher Biology Chapter 19 Symbiosis

Symbiosis • the co-evolved intimate relationship between organisms of 2 different species • 2 categories of symbiosis: • Parasitism- one organism (the parasite) benefits at the expense of the other organism (the host) which is often damaged/harmed • Mutualism- both organisms benefit from the interdependent relationship

Parasitism • Parasites have a limited metabolism • they cannot survive without contact with a host • they depend on the host organism in order to gain nutrition • the host is damaged or loses energy/materials • there has to be a balance between the defencemechanisms of the host and the damage caused by the parasite • the parasite does not want to cause its host to die • some parasites live and feed inside their host e.g. tapeworm, or outside their hoste.g. mosquito

Transmission • the movement of parasites from one host to another • can be through direct contact e.g. head lice passed by physical contact • release of resistant stages- they are able to survive adverse environmental conditions for long periods until they come into contact with a new host • use of a vector e.g. mosquitos carry Plasmodium, the unicellular organism that causes malaria

Parasite life cycles- Direct • Direct life cycle- eggs are shed and pass to a new member of the host species • this involves one species of host only • common with parasites living outside of the host • e.g. fleas and lice

Parasite life cycles- Indirect • Indirect life cycle- parasite uses a primary host as its site for sexual reproduction and an intermediate (secondary) host species is involved in its’ life cycle • A person (primary host) eats undercooked meat • a tapeworm which is attached to the wall of the intestine lays fertilisedeggs • animal eats food contaminated with human faeces (containing the fertilised eggs) • embryo is transported to muscle tissue (intermediate host) • The life cycle starts all over again

Advantages of using a secondary host (for info only) • Reproductive advantage- with the use of only a primary host, the parasite only uses sexual reproduction • this causes increased variation/adaptation • with the use of a primary and secondary host, the parasite undergoes asexual reproduction as well • this leads to increase variation/adaptation/population numbers, ultimately increasing the parasites’ chances of survival • Overall this makes it easier for the parasite to gain a primary host (so the advantage is in transmission too)

Higher Biology Chapter 19 Symbiosis- Mutualism

Mutualism(both organisms benefit) E.g. Cellulose Digestion in herbivores • cellulose is part of the cell walls of plant cells • many herbivores lack the genes for producing the enzymes required to digest cellulose, even though it is a huge part of their diet • instead, these herbivores have special gut chambers containing microbes that produce the enzymes to digest cellulose • the cellulose is broken down into simple sugars for the herbivore to use as its main energy source • the microbes receive protection, warmth and constant supply of food • this mutualistic relationship is of economic importance as humans rely on cattle/sheep (ruminants) for food/other products

Mutualism- continued(both organisms benefit) E.g. Coral Polyps • a coral polyp is unable to move from place to place • it secretes a hard skeleton which attaches it to the skeletons of earlier polyps (this forms a coral reef) • it has a mutualistic relationship with an algae called zooxanthella • the coral polyp can use up to 80% of the carbohydrate made by the algae for energy • in return the algae are provided with secure habitat and supply of the polyps’ nitrogenous waste which they convert to protein • coral reefs are known to have existed for over 200 million years, which proves the success of this symbiotic relationship

Read pages 292-295 Page 297 Q1-3

Starter Questions