Year 11 Biology: Predicting Consequences

• Predicting consequences in year 11 biology involves investigating the relationships between biotic and abiotic factors in an ecosystem. This includes assessing how predation, competition, symbiosis, and disease impact populations.

Trophic Levels

• Trophic levels demonstrate the hierarchical structure within an ecosystem.
• They show an organism's position in a food chain, food web, or biomass pyramid.
• Food chains exhibit the flow of energy in an ecosystem between organisms.
• Food webs consist of multiple food chains within ecosystems and display the roles of producers, consumers, and decomposers.
• Biomass pyramids display the total biomass (energy) at each trophic level. Biomass decreases as you move up the pyramid. 10% of energy is passed to the next level.

Population Sizes

• Population sizes are not constant due to various factors.
• Ecologists determine the impact of factors on a species' population size.
• Main factors affecting population size: predation, competition, symbiosis, and disease.

Predicting Population Dynamics: Predation

• Predators influence the distribution and abundance of their prey.
• Predation is a natural means of population control.
• Predator-prey relationships can fluctuate over time, with predator numbers mirroring prey abundance changes.
• High prey numbers lead to increased predator populations; however, as prey decreases, predator numbers decline due to food shortage.

Factors Affecting Predator-Prey Relationships

• Number of predators competing for the same prey.
• Availability of prey.
• Reproduction rate.
• Death rate (other than predation).
• Ratio of males to females.
• Size of an ecosystem.
• Seasonal behaviors (e.g., migration).
• Number of shelter sites available.

Predicting Population Dynamics: Competition

• Competition between species for resources affects reproduction and survival rates.
• Population fluctuations are linked to competing species and resources; if resources are abundant, competitor populations grow.
• More successful species outcompete others, leading to possible extinction of the unsuccessful. Long periods of decreased reproduction and increased deaths will eventually lead to the losing species being wiped out.
• Failing species sometimes can adapt by occupying a niche allowing survivial.

Predicting Population Dynamics: Symbiosis

• Symbiosis has significant effects on life: contributing to evolutionary diversification, development of new species (symbiogenesis), and new capabilities and organisms evolve "fitness".
• Symbiotic relationships maintain biodiversity by creating new ways to exploit resources.

Symbiosis: Biodiversity

• Symbiosis increases biodiversity, making ecosystems more resilient, like coral reefs, which depend on the relationship between coral and algae.
• Coral reefs provide a unique environment for various fish and marine invertebrates.

Symbiosis: Symbiogenesis

• Eukaryotic cells acquired aerobic respiration around 1-2 billion years ago from primitive mitochondria-like organisms. This is an example of symbiogenesis, where genetic material is incorporated into two separate species.

Symbiosis: Fitness

• Legume plants have an association with nitrogen-fixing bacteria in their root nodules.
• The plant supplies the bacteria with nutrients, and the bacteria supply nitrogen to the plant.
• Some bacteria "cheat" by acquiring sugar without providing nitrogen back.

Predicting Population Dynamics: Diseases

• Diseases are processes that affect tissue function in living organisms due to infectious and non-infectious causes.
• Major infectious diseases are environmental threats in wild ecosystems.
• Disease-causing agents exist, and outbreaks occur when a pathogen enters a host population or is given a selective advantage.
• Climate change, deforestation, and water/soil degradation increase breeding sites for vectors, increase resistance in pathogens (pesticides), and reduce species disease resistance.
• Changes in environmental factors leading to stress compromise barriers to pathogen invasion. Outbreaks alter food webs and dramatically reduce species numbers.

Disease: Case study

• Devil facial tumor disease (DFTD) is a transmissible cancer spreading through Tasmanian devil populations via social interactions like biting.
• The body does not recognize the cancer cells as foreign, and the disease is often fatal within 6 months.
• Vision impairment and food shortages commonly affect the animals.
• Without intervention, Tasmanian devils could face extinction in 25 years.
• The "Save the Tasmanian Devil" program was created in 2003, and scientists are finding more succesful treatments for the disease.