Lessons 3–4 · 2 lessons · A. G‘afurov, A. Abdukarimov, J. Tolipova, O. Ishankulov, M. Umaraliyeva, I. Abdurahmonova. Biology Grade 11, 1st edition. Sharq Publishing and Printing Joint-Stock Company, Tashkent, 2018
4
Components of ecosystems
Textbook: pp. 18–22
GoalDescribe the composition of an ecosystem (biotope, biocenosis), producers, consumers and decomposers, and the properties of a biogeocenosis (self-regulation, succession).
An ecosystem consists of a biotope and a biocenosis; the non-living part of the biotope, the ecotope, comprises climate factors (climatotope) and soil (edaphotope). The organisms of a biocenosis fall into three functional groups. Producers (green plants, photosynthetic and chemosynthetic bacteria) build organic compounds from inorganic matter; consumers (animals, parasitic plants) feed on ready-made organic matter; reducers (saprotrophic bacteria and fungi) break dead remains down to mineral substances and return them to producers. A biogeocenosis renews and regulates itself: for example, if rodents multiply, predators multiply too, then rodents decline – numbers oscillate and stay near an average. The greater the species diversity, the higher the stability. Periodic (daily, seasonal) changes return the community to its starting state, while progressive changes lead to one biocenosis replacing another – ecological succession.
Worked examples
In a mountain ecosystem the juniper is a producer, the wild goat and the eagle are consumers, and saprotrophic soil fungi are reducers. If the birds and rodents that eat seeds and fruits disappeared, seed dispersal and number control would be disturbed.
A lake slowly dries; marsh plants appear at the shore, then meadow, then shrubs: one community is replaced step by step by another – this is succession. The lake changing from summer to winter and returning to its former state in spring is a periodic change.
Class activity
Imagine that only the reducers are removed from an ecosystem. In groups, draw the chain of consequences (dead leaves, mineral substances, plant growth) in 10 minutes and compare with another group.
Practice
1
Distinguish producer, consumer and reducer.
A producer creates organic matter; a consumer feeds on ready-made organic matter; a reducer breaks dead remains down to minerals.
2
Which group: cotton plant, brown bear, putrefying bacterium, blue-green alga (cyanobacterium), sulphur bacterium?