LWB: Lesson - Introduction to Biodiversity (Topic 2.1) ๐Ÿ“–

โณ Estimated Reading Time: 6 - 8 minutes

Learning Objective

Explain levels of biodiversity and their importance to ecosystems. 

 

Biodiversity


Biodiversity is the variety of life on Earth at all levels, from genes to species to ecosystems. It is the result of evolution, which is the process of natural selection acting on genetic variation. Biodiversity is important for the health and functioning of ecosystems, as it provides resources, services, and resilience to environmental changes.

There are three types of biodiversity - genetic, species, and habitat diversity. Explore the tabs below to learn more about each type of biodiversity. Each type is critical to biodiversity.

Genetic Diversity

Genetic diversity is when there are a variety of genes present in a reproducing population. Genes occur in different variants (alleles). The more alleles in the population, the more genetic diversity. Individuals carry two copies of every gene, one from each parent. Different populations have different alleles for the gene. Each species has its own set of alleles. Each ecosystem has its own set of genetic diversity. Migration between populations and ecosystems can change the genetic diversity of an area.

The graphic depicts genetic diversity, highlighting that a greater variety of alleles increases diversity. Each individual inherits two gene variants, one from each parent. Different populations and species possess unique alleles, contributing to an ecosystemโ€™s genetic variety. Migration can alter an areaโ€™s genetic diversity.
 

Genetic diversity is essential for the resilience and adaptability of ecosystems to environmental changes, enabling some individuals to better survive and reproduce in response to environmental pressures, such as climate fluctuations or new predators. In simpler terms, it's like having a toolbox with a wide range of tools โ€“ the more diverse the tools, the better equipped you are to handle different challenges. Genetic diversity can be influenced by natural selection, mutation, gene flow, and genetic drift. Genetic diversity can be measured by the number of different alleles, genotypes, or phenotypes in a population. 

There are several factors influence genetic diversity within populations. Let's take a look at the most common influences on genetic diversity:

Population Size ๐Ÿ‘จโ€๐Ÿ‘ฉโ€๐Ÿ‘งโ€๐Ÿ‘ฆ (click to reveal)
an image of a population with many colored alleles in a bottle. A few alleles are poured out into a jar during the bottleneck event, leaving the surviving population without several of the alleles found in the original population.
A population bottleneck is a sudden reduction in the size of a population due to a catastrophic event, such as a natural disaster, disease, or human activity.

One key factor is population size โ€“ smaller populations are more susceptible to genetic drift, a random change in allele frequencies over time. Genetic drift can lead to a loss of diversity, especially in isolated or bottlenecked populations.

This can reduce the genetic diversity of the surviving population, as some alleles may be lost or become more common. Because the alleles that are lost in during the event are not necessarily those least suited to their environment, a bottleneck can reduce a species' survival.

With average global temperatures increasing, cold environments are warming, causing ice to melt. If there was a polar bear that had slightly thinner fur or slightly darker fur, it might be better adapted to a warming environment.

A polar bear walking on ice
Polar bears are adapted to living in very cold, icy environments.

Because it would not get too hot in a warmer environment and would be better at blending into the new environment, making it easier for it to catch prey. This polar bear would be better adapted to the changing environmental conditions than a โ€œregularโ€ polar bear, shifting the genetic diversity of the polar bear population. However, because polar bear populations are shrinking, the likelihood of these genes being in the polar bear population also shrinks.

Migration, or gene flow, can also impact population size. When individuals move between populations, they bring new genetic material, increasing diversity. Conversely, isolation can limit gene flow, potentially leading to increased genetic divergence between populations. 

 

Mutations ๐Ÿงฌ (click to reveal)
a drawing of a monkey with a long tail hanging from a tree by its forelimbs
Long tails help primate escape predators and reproduce in forests.

Mutations, the random changes in DNA sequences, play a vital role in contributing to genetic diversity. While some mutations may seem unwelcome or harmful, others can actually introduce beneficial traits that enhance a population's ability to adapt to its environment.

It's like a genetic lottery - sometimes you get changes that help you survive and thrive!

The process of natural selection kicks in by favoring individuals with these advantageous traits, ensuring that they pass on their genes to the next generation.

This cycle not only influences the survival of a species but also helps in maintaining or altering genetic diversity based on the unique demands of the organism's surroundings

For example, a primate born with an especially long tail might be able to escape predators more quickly, making it more likely to survive and reproduce, passing on its long tail gene. If this same long-tailed primate was born in a desert or an ecosystem where the long tail was a liability, not a benefit, the long-tailed primate would likely die early, without reproducing, reducing the likelihood that the long-tail gene would be passed on in the desert population.

 

 

Essential Knowledge

Biodiversity in an ecosystem includes genetic, species, and habitat diversity.

The more genetically diverse a population is, the better it can respond to environmental stressors.

A population bottleneck can lead to a loss of genetic diversity. 

Species richness refers to the number of different species found in an ecosystem.

Ecosystems that have a larger number of species are more likely to recover from disruptions.

Loss of habitat leads to a loss of specialist species, followed by a loss of generalist species. It also leads to reduced numbers of species that have large territorial requirements.

 

AP Exam Tip

As we study how humans affect the environment during this course, you should always think back to how that disruption can affect the biodiversity of the area.

 

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