Problem 14 - Biology Today and Tomorrow with Physiology

Question

Match each term with its most suitable description. $$\begin{array}{cc}\text{______carrying capacity} && \text {a. change in birth and death rates with industrialization}\end{array}$$ $$\begin{array}{cc}\text{______logistic growth} && \text {b. group of individuals born during the same period of time}\end{array}$$ $$\begin{array}{cc}\text{______exponential growth} && \text {c. population growth plots out as an S-shaped curve}\end{array}$$ $$\begin{array}{cc}\text{______demographic transition} && \text {d. largest number of individuals sustainable by the resources in a given environment}\end{array}$$ $$\begin{array}{cc}\text{______limiting factor} && \text {e. population growth plots out as a J-shaped curve}\end{array}$$ $$\begin{array}{cc}\text{______cohort} && \text {f. essential resource that restricts population growth when scarce}\end{array}$$

Step-by-Step Solution

Answer

a: demographic transition, b: cohort, c: logistic growth, d: carrying capacity, e: exponential growth, f: limiting factor.

Step 1: Analyzing 'carrying capacity'

The term 'carrying capacity' refers to the largest number of individuals that can be sustained by the available resources in a given environment. Therefore, it matches with description 'd'.

Step 2: Analyzing 'logistic growth'

'Logistic growth' describes a population growth pattern that plots out as an S-shaped curve. It considers the carrying capacity of the environment and matches with description 'c'.

Step 3: Analyzing 'exponential growth'

'Exponential growth' is when a population grows in proportion to its current size, resulting in a J-shaped curve. Thus, it matches with description 'e'.

Step 4: Analyzing 'demographic transition'

'Demographic transition' involves changes in birth and death rates usually associated with industrialization and development, matching it with description 'a'.

Step 5: Analyzing 'limiting factor'

A 'limiting factor' is an essential resource that restricts population growth when it is scarce, aligning with description 'f'.

Step 6: Analyzing 'cohort'

A 'cohort' is a group of individuals born during the same period of time, which corresponds to description 'b'.

Key Concepts

Carrying Capacity

In ecology, the term "carrying capacity" refers to the maximum number of individuals of a particular species that an environment can sustainably support. This is not a fixed number, but rather a dynamic one, as it depends on the availability of essential resources like food, water, and habitat, all of which fluctuate over time.

When a population reaches its carrying capacity, growth essentially stops because the resources can no longer support additional individuals. If a population exceeds its carrying capacity, individuals may suffer from starvation, increased mortality rates, and reproductive failure, often leading to a population decline back to sustainable levels.

Logistic Growth

Logistic growth is a model of population growth that incorporates the concept of carrying capacity. Unlike exponential growth that assumes unlimited resources, logistic growth portrays a more realistic model where growth slows as the population reaches the environment's carrying capacity.

This pattern creates an S-shaped or sigmoid curve. Initially, the population grows exponentially; however, as it approaches the carrying capacity, the growth rate declines, eventually stabilizing when the population size is supported by the available resources.

This model underscores how natural population growth is regulated by internal and external environmental factors.

Exponential Growth

Exponential growth describes how populations grow rapidly when resources are abundant and their growth is unconstrained. With this model, the population size increases at a constant rate over time, creating a J-shaped curve.

In nature, exponential growth is often unsustainable in the long term because resources become limiting at some point. However, under ideal conditions with no limiting factors, such as enough food and no predators, populations can experience exponential growth, at least temporarily.

It is important to compare this with logistic growth, where resource limitations eventually slow down and stabilize population growth.

Demographic Transition

The demographic transition is a model that describes the transformation of a population from being high in birth and death rates to low in birth and death rates. This process typically occurs in human populations as they transition from pre-industrial to industrialized economies.

The demographic transition involves several stages:

• The pre-transition phase, where both birth and death rates are high, keeping the population size stable.
• The transition phase, where death rates drop due to improvements in healthcare and sanitation, while birth rates remain high, leading to population growth.
• The post-transition phase, where birth rates also decline, stabilizing the population at a lower growth rate.

This concept helps explain the population trends in different regions and stages of development.

Limiting Factor

A limiting factor in ecology refers to a variable that can constrain the growth of a population once it becomes scarce. It could be any essential element or resource such as food, water, shelter, or even space.

Limiting factors can both naturally occur or result from human activities. A classic example is the food supply, which limits how many individuals a certain area can support. When a limiting factor is exhausted, it results in resource competition, increased mortality rates, and decreased birth rates, pulling the population back to sustainable levels.

Understanding limiting factors is crucial for managing wildlife populations and conservation efforts.

Cohort

A cohort is a term used to represent a group of individuals who experience the same event within the same time period. In population biology, it's most often used to describe groups of individuals born at the same time.

Cohorts are useful for studying specific characteristics and life events, such as survival rates, reproductive success, and growth patterns, across the different stages of their life cycle.

This concept helps scientists and demographers analyze population dynamics over time and make projections about future population trends based on observed data patterns.