Problem 7 - Animal Physiology: From Genes to Organisms

Question

Cheetahs are highly susceptible to diseases such as feline infectious peritonitis (FIP), which kills less than \(10 \%\) of other cats but \(50 \%\) of cheetahs. Cheetahs are nearly identical genetically, apparently due to a crash in population numbers perhaps 10,000 years ago. Explain why low genetic diversity in these cheetahs and also in inbred domestic animals makes acquired immunity less effective.

Step-by-Step Solution

Answer

Low genetic diversity limits the variety of immune responses, making cheetahs and inbred animals more susceptible to diseases.

Step 1: Understanding Genetic Diversity

Genetic diversity refers to the total number of genetic characteristics in the genetic makeup of a species. It is important because it enables a population to adapt to environmental changes, such as diseases or climate changes.

Step 2: Low Genetic Diversity in Cheetahs

A population with low genetic diversity has very similar genes among all its members. This lack of variation can result in an inability to adapt to new or changing environments, as there are fewer alleles (different versions of genes) to help resist diseases.

Step 3: Impact on Acquired Immunity

Acquired immunity is the immune system's ability to learn and remember specific pathogens, leading to a more effective response upon repeated exposure. High genetic diversity allows a wider range of immune responses to potential infections.

Step 4: Low Diversity and Immunity

With low genetic diversity, the immune response lacks variety, meaning fewer types of pathogens can be effectively fought off. Cheetahs, due to their genetic similarity, fail to develop broad immunity, making diseases like FIP more deadly.

Step 5: Comparison to Inbred Domestic Animals

Inbreeding in domestic animals also reduces genetic diversity. Like cheetahs, inbred populations of domestic animals show weaker immunity, making them more susceptible to diseases due to the reduced variation in their immune system genes.

Key Concepts

Genetic Diversity

Genetic diversity is the range of different genetic traits within a species.
It's like having a variety of tools in a toolbox.
With more tools (genetic traits), organisms can handle many different challenges.
High genetic diversity makes populations strong against changes.
When a disease strikes, genetic diversity ensures some individuals have immune systems capable of fighting off the infection.
This diversity helps the species thrive over time.
In cheetahs, however, the genetic toolkit is small.
A past population crash reduced their genetic diversity, limiting their chances against new diseases.

Acquired Immunity

Acquired immunity is the body's ability to remember past infections and fight them off more efficiently the next time they're encountered.
Think of it as the immune system being a great student.
It 'learns' from previous battles with pathogens and gets better at defeating them.
When a pathogen is encountered for a second time, the immune response is faster and stronger.
This system works best in populations with high genetic diversity, as the immune system genes are varied and better equipped to recognize many different pathogens.

Inbreeding Effects

Inbreeding happens when closely related individuals mate and produce offspring.
This reduces genetic diversity, resulting in a less varied genetic toolkit.
In domestic animals and cheetahs, inbreeding means many individuals share similar immune system genes.
This uniformity can lead to weaker immune responses.
Without different alleles, there's less chance to fight off various diseases effectively.
Inbred populations may show more inherited diseases and struggle with overall health issues.

Disease Susceptibility

Disease susceptibility refers to how likely an organism is to catch a disease.
When genetic diversity is low, disease susceptibility increases.
Pretty much like in cheetahs and some inbred domestic animals.
These animals don't have enough different immune genes to combat the variety of pathogens they might face.
For instance, feline infectious peritonitis (FIP) is much deadlier in cheetahs because their immune systems aren't diverse enough to fight it effectively.

Cheetah Genetics

Cheetah genetics are unique due to a historic bottleneck event.
This event drastically reduced their population size, causing today's cheetahs to be almost genetically identical.
This lack of genetic diversity affects their survival.
Cheetahs struggle with diseases, lower fertility rates, and other health issues tied to their genetic makeup.
Understanding their genetic challenges helps in conservation efforts.
It highlights the importance of maintaining genetic diversity in any species to ensure long-term resilience.