Species interactions

1. Species interactions • Use pictures to construct species webs for different ecosystems • Desert • Mangrove • Coral reef • Arctic ocean and pack ice

2. Types of species interaction • Predator prey • Grazing • Intra-specific competition • Inter-specific competition • Decomposer organisms • Host parasite • Host pathogen • Commensalisms • Symbionts

3. Predator prey relationships • The classic ecological explanation of these is that predator populations are controlled by the availability of prey. • This is fair in natural ecosystems but must be qualified. • In unnatural ecosystems prey may have no refuges and be completely consumed before the predators starve to death

4. Natural vs managed ecosystems Natural lowland river in England River straightened for drainage The rich variety of habitat structure in this river allows prey species to evade predators. In the drainage ditch the prey fish have nowhere to hide and the predator can catch and eat them all.

5. Farming • Farming maintains unnaturally high concentrations of prey/host species • This is why farmed animals are very vulnerable to natural predators and disease

6. Predator prey relationships • Read the text then answer these questions • 1. Name three distinct types of predator prey relationships. • 2. Which predator prey relationship did Volterra observe and what did it show? • 3. Why were ecologists able to model snowshoe rabbit-canadian lynx populations over such an extensive time period? • 4. Why do you think the predatory protozoan was able to annhiliate the Paramecium in laboratory cultures?

7. Predator prey relationships • 5. What do you understand by spatial heterogeneity? • 6. Why, after achieving such dramatic reductions in prickly pear numbers could the moth not fully eradicate it from Australia? • 7. Both moth and prickly pear live in central America – how come the prickly pear is so common here!? • 8. How does a keystone predator act to maintain species diversity?

8. Cattle as key stone predators Grazing density / hectare Plant species /m2 • 0 cows • 1 cow • 2 cows • 3 cows • 4 cows • 5 cows • 5 • 27 • 26 • 14 • 12 • 6 Summarise the impact of cattle grazing on species biodiversity in the habitat. In what ways may the cattle grazing activity improve species diversity?

9. Intraspecific competition • Competition between members of the same species within a population. • Darwen thought about elephants. • Darwin calculated that in elephants, which are among the slowest breeding land mammals, if all of the potential young of a single female survived and reproduced at the same rate, after 750 years the descendants of this single mother could number 19,000,000!

10. There are not 19million elephantsWhy not? • Competition for food and resources • Too many elephants and they would eat all the food. Then they would starve. • Why is this so important? • All species are under constant pressure due to intraspecific competition. Only the fittest can survive! • This is called survival of the fittest • Any that have extra benefit from a better gene will be sure to survive. This can lead to an increase of that gene in the population. • This is the basis of evolution.

11. Interspecific competition • Competition between species • This can lead to one species dominating – think of the rocky shores • Under natural conditions this is reduced allowing several species to coexist. • This is because each species has a different niche • Or one species is prevented from dominating • But change the environment and this balance can be lost

12. Interspecific competition in immigrant species • Around the world different often related species occupy the same niche • Red and Grey squirrels

13. Grey squirrels were introduced to Britain and have nearly replaced the native red They have done this because they can make better use of available food, are bolder and more willing to forage on the ground and are immune to a disease they carry

14. Similar species • Many similar species do coexist • How? • By avoiding inter-specific competition • Strategies • Different food • Different tolerances to environmental factors • Different abilities to avoid predators • Different breeding requirements • Different requirements of light, temperature, shade etc.

15. Research • Look at an assemblage of similar species found in a geographical area • Explain how they coexist • Produce a power point to show how they reduce inter-specific competition. • E.g. antelopes on the africansavanah

16. Decomposers • Many organisms eat solely dead and decaying material • These organisms are fundamental in all ecosystems • Some are very specific only occupying rotting material at specific stages of its decomposition • The White backed woodpecker feeds only on invertebrates of decaying wood.

17. Invertebrates • There are more than 1700 different invertebrate species in Britain and Ireland which are dependent on decaying wood in order to complete their life cycles • Many are rare due to the lack of old and rotting trees. We have little natural woodland!

18. Important decomposers • Carrion eating birds • Flies and their larvae • Beetle species • Worms • Fungi • Bacteria

19. Closer relationships • Some species relationships are physically much closer than predator and prey. • Some benefit both species, others only one species whilst in others one species is harmed. • These relationships are referred to as symbiosis, especially if both species benefit • Almost nothing on earth exists without symbiosis • We have a symbiotic relationship with our gut bacteria.

20. Symbiosis • Both species benefit from close association • May be endo-symbionts with one species living within the tissue of another • E.g nitrifying bacteria in the root nodules of leguminous plants, algae living inside reef building corals. • Others are ecto-symbionts where one lives on the other: e.g. gut bacteria or lice on the skin or barnacles on whales • Mutual symbionts include such things as cleaner fish and shrimps and the fish they service.

21. Commensalism • Means literally feed at the same table. • This is a loose association of species. Usually one species benefits whilst the other is neutral. • Cattle egrets and • Cattle. The animals stir • up and attract insects • that the egrets feed on. • The cows are unaffected.

22. Mutualism • Both species interact in a way which is beneficial to both. • Examples include the bacteria in the guts of cattle that help digest grass or in the guts of termites that help digest wood • Insects and birds pollinating flowers – nectar is produced to encourage this mutualism • Oxpeckers removing ticks from large grazing animals • Cleaner fish and shrimps.

23. Obligate mutualism • Two species are unable to survive without the other • Most orchids require a fungal mycorrhizal association with their roots to be able to grow.

24. Parasitism • One organism benefits, one is harmed. Disease causing organisms are all parasites • Klepto parasitism one animal steals another’s food: • The frigate bird:

25. Ectoparasitism • Ticks suck blood

26. Gut parasites – technically ectoparasites • Tapeworm Roundworms (nematodes)

27. Endoparasites • Found in the body tissue e,g flukes

28. Research a parasitic disease • Learning focus: writing extended essays • Task: Identify a parasitic disease caused by a multicellular or single cell organisms not including virus or bacteria • Describe the life cycle of the disease causing organisms • Identify the symptoms, incidence, and mortality of the diseases. • Describe treatment and outcomes. Describe control measures • Include references