1. 1 CfE Higher Biology 3.5 Symbiosis

2. 2 Key areas: 5. Symbiosis a) The costs, benefits and ethics of providing different levels of animal welfare in livestock production. Behavioural indicators include stereotypy, misdirected behaviour, failure in sexual or parental behaviour, altered levels of activity. (b) Observing behaviour (ethology). The observed behaviours of domesticated animals in natural or semi-natural settings. Information from these studies can be used to improve the environment for domesticated animals. The use of preference tests and measurements of motivation in animal welfare studies.

3. 3 Symbiosis ‘Living together’: a close association of two dissimilar organisms Mutualism Commensalism Parasitism Are the main forms of symbiosis. Interactions between species may be described as being positive, negative or neutral. POSITIVE: benefits species NEGATIVE: harms species NEUTRAL: no effect on species In symbiosis at least one species will gain through the relationship.

4. 4 Parasitism An organism that lives in or on another living organism. It obtains from that organism either all or part of its organic nutrients. This is usually to the detriment of its host. There are two types of parasites: OBLIGATE PARASITES: depend on a host organism in order to survive (viruses) ENDOPARASITES: inside the body ECTOPARASITES: outside the body FACULTATIVE PARASITES: Do not need a host to survive as they can live in or out with a host organism (nematode worm).

5. 5 Obligate Parasites Cyst (Entamoeba histolytica) Humans are the primary host for this pathogen which is spread via the anal to oral route. Normally acquired from contaminated water and food. Causes amoebic dysentry; bloody stools/ diarrhoea/abdominal pain. Cysts are shed in faeces. Cyst (Balantinium coli) Causes diarrhoea in humans. Pig’s faecal matter is normally a sources of this disease and it can spread from person to person by contaminated water.

6. 6 Obligate Parasites Liver fluke (Fasciola hepatica) Require snails as intermediate hosts. Humans and other mammals acquire the organism by eating cyst-contaminated water plants, such as watercress. The cyst releases immature flukes which migrate to the liver and gallbladder. Pinworm (Enterobius vermicularis) Infests young children. The worm is spread by the consumption of an egg that contaminates food. It reproduces in he intestinal tract, with the adult laying her eggs on the anus. Contaminated fingers, from scratching, are the usual route for re-infestation.

7. 7 Obligate Parasites Malaria (Plasmodium falciparum) This is spread by the bites of a mosquito and occasionally by contaminated needles (blood.) Human liver/ red blood cells and mosquito salivary glands are needed for the life cycle. Hemoflagellate (Trypanosoma brucei) Causes sleeping sickness. It is spread by the bite of a tsets fly, which transfers the organism from an alternative host (like a cow.)

8. 8 Facultative Parasites Saprolegnia: Is the main genus of water moulds responsible for significant fungal infection in freshwater fish and eggs. Results in viable white and grey patches. Above: Saprolegnia (water mould) Right: Salmon infected with Saprolegnia

9. 9 Parasites Parasites need: Nutrients Water Gaseous environment This is why most parasites will not cause the host cell to die, it merely exploits its resources. It may cause some damage to the host though. If the host cell does die this is usually at the end of the parasites life cycle when the resources that the host has is no longer needed. If the host cell dies while the parasite is still needing it, then the parasite has to be able to infect a new host quickly. This is achieved through 1. Direct contact 2. Resistant stages3. Secondary host species/vectors

10. 10 Transmission of Parasites DIRECT CONTACT: Jumping. Ectoparasites such as fleas will move from one individual to another when there is direct contact between them. Crowding roosts, suckling young, communal habitats all provide opportunities for parasites in this way. Other examples: HEADLICE MEASLES COMMON COLD

11. 11 Transmission of Parasites RESITANT STAGES: Many parasites have dormant resistant stages which can remain viable for the host for long periods of time. (WATER……STALKS OF GRASS) When these parasites are consumed by an appropriate organism, the parasites activity will be induced. LIVER FLUKE: in streams and ponds for more than a year before being washed into vegetation. Then they will be taken up by grazing animals.

12. 12 Transmission of Parasites SECONDARY HOSTS SPECIES AND VECTORS Vector means a carrier. These organisms usually help to transfer a parasite from its primary host to another. INSECTS and TICKS! By infecting different hosts at different stages of the parasite life cycle it will gain in a variety of ways: Nutrition/development from primary hosts Widespread dispersal from secondary hosts. Mosquitoes (vector) and Malaria (parasite).

13. 13 Transmission of Parasites VECTOR TRANSMISSION: Mouth parts are fairly essential to the vector; most parasites are transferred via the mouth when sucking blood ‒ FLEA BITES Ingesting vectors ‒ TAPEWORMS Plants are also affected. Aphids transmit viruses when they are feeding. Wind/ Water transmission; used for reaching their new host ‒ BLOOD FLUKE

14. 14 Transmission of Parasites Questions 1. Using the example of the ‘blood fluke’, describe the importance of humans and the effects of this parasite on humans. Refer to the different stages in its life cycle. 2. Plasmodium falciparum causes malaria. Describe the life cycle of this parasite.

15. 15 Pork and Beef tapeworms

16. 16 Mutualism This partnership benefits both partners. Some mutualistic relationships are so important that they affect all life-forms. Mycorrhizal associations (fungus): aid plants taking up nutrients in the soil and in return will receive sugars from their hosts. Legumes: rely on nodule-forming associations between their roots and micro-organisms to fix nitrogen. In return these nitrogen fixing plants are essential for succession to occur. Lichens: Mutualistic associations between alga and fungus. The fungus provides strength, protection and structure (including structures to anchor the plant/the taking in of water and extraction of nutrients.) the alga provide food by photosynthesis.

17. 17 Endosymbiotic origin evidence Mitochondria & Chloroplasts 1.Has its own DNA which is circular. 2.Ribosomes are similar to prokaryotes. 3.Size and structure. 4.Has enzyme and transport systems. 5.Replication is similar to bacteria. Questions 1.Describe the principles behind why mitochondria and chloroplasts are thought to have evolved by mutualism. 2.Using the list of characteristics adjacent, describe in more detail why mitochondria and chloroplasts are thought to have evolved from prokaryotes.