IB SL BIOLOGY TOPIC 4 ECOLOGY COMPLETE STUDY GUIDE 2023

IB BIOLOGY TOPIC 4 ECOLOGY COMPLETE STUDY GUIDE 2023 Topic 4.1: Ecology – Species, communities and ecosystem The continued survival of living organisms including humans depends on sustainable communities. • Understanding: Species are groups of organisms that can potentially interbreed to produce fertile offspring.  Species: groups of organisms that can potentially interbreed to produce fertile off-springs  Crossbreeding: interbreeding between different species with off-springs almost always infertile • Understanding: Members of a species may be reproductively isolated in separate populations.  Speciation: process in which one species is reproductively isolated into different populations they develop into different species where they are unable to produce viable off-springs Type of mechanism Description Example Geographical isolation Population is separated as the environment imposes a geographical barrier Natural disasters, continental shift Ecological isolation Population is separated by occupying different habitats (disruptive evolution) Tree and mud lizards Temporal isolation Population is separated through reproducing at a different season/time Winter and summer plants Behavioural isolation Population is separated through differing in their respective mating rituals Birds of paradise • Understanding: Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).  Autotrophs: organisms that synthesize their won organic molecules from simple inorganic substances  Heterotrophs: organisms that obtain organic molecules from other organic organisms  Mixotrophs: organisms that has both autotrophic and heterotrophic means of nutrition (e.g. Chlamodomonas or Euglena) • Understanding: Consumers are heterotrophs that feed on living organisms by ingestion.  Consumers: heterotrophic organisms that feed on living organisms by ingestion • Understanding: Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.  Detritivores: heterotrophic organisms that feed on organic nutrients from detritus (dead organic matter) by internal digestion • Understanding: Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.  Saprotrophs: heterotrophic organisms that feed on organic nutrients from detritus (dead organic matter) by external digestion • Understanding: A community is formed by populations of different species living together and interacting with each other.  Community: populations of different species living and interaction with each other  Examples of community interactions: symbiosis (mutualism, parasitism), predation, disease agents • Understanding: A community forms an ecosystem by its interactions with the abiotic environment.  Ecosystem: interaction of the community with the abiotic environment  Abiotic factors: non-living, physical components of an ecosystem (e.g. light, wind, pH, salinity, temperature)  Biotic factors: living components of an ecosystem (e.g. symbiosis, mutualism, predation) • Understanding: Autotrophs obtain inorganic nutrients from the abiotic environment.  Autotrophs: obtain all nutrients from the abiotic environment (e.g. carbon, nitrogen, sodium etc.)  Heterotrophs: obtain most nutrients from food, but they obtain many inorganic nutrients from the abiotic environment (e.g. sodium) • Understanding: The supply of inorganic nutrients is maintained by nutrient cycling.  Nutrient cycles: cycle process in which organisms absorb, use and return elements from and to the abiotic environment (e.g. carbon)  Nutrients and energy: energy is able to enter and leave ecosystems while nutrients can only be cycled • Understanding: Ecosystems have the potential to be sustainable over long periods of time.  Requirements for ecosystem sustainability