A species

Defining a species

Organisms within a species:

• Share similar characteristics and behaviours, often occupying the same ecological niche.

• Can interbreed to produce fertile offspring.

However, defining a species can sometimes be challenging:

• Convergent evolution can cause unrelated organisms to develop similar features and ecological niches due to adaptation to similar environments.

• In artificial environments, like zoos or labs, some organisms that wouldn’t normally breed in the wild may interbreed. Additionally, closely related species, such as horses and donkeys, can sometimes mate to produce hybrids (e.g., a mule), though these offspring are usually infertile.

Courtship behaviour

Courtship behaviour plays an essential role in reproductive success. Controlled by genes, courtship behaviour varies across species, allowing individuals to identify members of their own species. Members of the same species will exhibit the same courtship patterns, while different species display distinct behaviours. Courtship behaviour:

• Ensures that animals recognize members of their species.

• Helps attract a mate of the opposite sex.

• Identifies a mate capable of breeding.

• Strengthens pair bonds to aid in raising offspring.

The more similar the courtship behaviours between two organisms, the more closely related they are, indicating shared ancestry.

Quantitative investigations of variation

Studying variation within a species involves:

• Collecting random samples from a population to ensure representative data.

• Calculating the mean of the collected data and its standard deviation.

• Interpreting means and standard deviations to understand the distribution of characteristics.

Scientists often represent their data graphically, expecting a normal distribution (bell curve) in the results. Standard deviation indicates the spread of data around the mean. When comparing populations, standard deviation can be shown with error bars on graphs. If error bars for one variable do not overlap with those for another, there may be a significant difference between the means of the sampled populations.

Definitions