Introduction to Ecology

Introduction to Ecology

• Ecology studies the interactions between organisms and their environments.
• Biogeography aims to understand the distribution and abundance of organisms on Earth.
• Ecology combines multiple scientific fields like Zoology (animals), Botany (plants), Environmental science (surroundings), and Microbiology (microbes).
• Demography studies populations through birth, death, and growth rates.
• Biodiversity refers to the variety of organisms in the biosphere that are affected by speciation and extinction rates.
• An endangered species means an organism is at risk of extinction.
• Preserves are areas designated to conserve endangered species.
• An endemic species exists only in a certain place because of geographic isolation.
• Understanding the impact of humans on the environment informs sustainable practices.

Organization Levels

• All matter consists of atoms that contain protons (+), neutrons (0), and electrons (-).
• Elements are the name of an atom based on their reactivity.
• Molecules are atoms paired to fulfill the Octet Rule and can be called compounds if the atoms are different elements.
• Macromolecules are large organic molecules that include carbohydrates, lipids, proteins and nucleic acids.
• Organelles are sub-cellular "organs" with different structures and functions.
• Cells are the basic unit of structure and function of life, like unicellular organisms (bacteria and archaea) or multicellular organisms (plants and animals).
• Tissues are clusters of cells with similar functions, such as types in plants (dermal, vascular, and ground) or in humans (epithelial, connective, nervous, and muscular).
• Organs consist of different types of tissues working together.
• Organ systems are groups of organs performing closely related functions, like digestive, excretory, respiratory, circulatory, lymphatic, immune, integumentary, nervous, muscular, skeletal, endocrine, and reproductive.
• An organism is an individual living thing.
• A population includes all members of a species in a given place.
• A community is multiple species interacting in an area.
• An ecosystem includes all living organisms and the abiotic environment they live in (ocean, freshwater and terrestrial biomes).
• The biosphere includes all ecosystems on Earth.

Demography

• Mathematics informs the study of interactions among living things and how environments affect abundance, distribution, density, and life strategies.
• Demography is the statistical study of population changes that investigates how populations respond to fluctuations.
• Populations include individuals of the same species living within a specific area.
• Population size is dynamic and fluctuates based on biotic (alive) and abiotic factors.
• Discussions will focus on changes in the environment, natural disasters, and competition for resources.

Population Size

• Population size (N) is the total number of individuals.
• The U.S. Census Bureau conducts a full census every 10 years, but local data is routinely estimated.
• Miami-Dade County has 2,687,568 people.
• Increases in population size occur through an increased birth rate.
• An increased birth rate can be caused by fulfilling basic needs by accessing space, water, and food.
• A larger population provides more potential reproductive pairings.
• A population with members that are closely clustered,
• A population with a higher female to male sex ratio, or a high percentage of individuals in reproductive age ranges also increase birth rates.
• Population size can also increase from a reduced death rate.
• Migration, including immigration (individuals entering) can increase population size.
• Emigration (individuals leaving) reduces population size.

Quadrats

• A Quadrat is a method of estimating population size.
• The area of interest is broken into equal-sized squares known as quadrants.
• Counting is performed in selected quadrants.
• Individuals are counted within the boundaries of each quadrant.
• An average of all counted quadrants is calculated.
• Estimating the population size: Average number of individuals multiplied by the total number of quadrants.
• For example, to find how many of an oak tree is present in a forest, divide the forest in a grid of 3 x 4 with equal quadrants.
• If two quadrants are found to have 36 oak trees, and the other had 34.
• The estimated population is as follows: (36+34)/2 = 35, 35 x 12 = 420 oak trees

Sample Problem Using Quadrats

• A quadrat is a method of estimating the population size.
• Divide into equal quadrants.
• Count randomly chosen quadrants.
• All individuals are counted.
• The average of the counted quadrants is multiplied by the total number of quadrants.
• For example, the estimate of elm trees present in a forest too large to count is done by dividing it into a grid of 5 x 5.
• Four quadrants that are selected have tree totals of 658, 642, 664 and 648.
• The calculation to determine quantity: (658 + 642 + 664 + 648)/4 = 653, with a final estimated number of 653 x 25 = 16,325 elm trees.
• Limitations include inaccurate averages and an inaccurate estimate if organisms aren't roughly equally spread among the quadrants.

Mark & Recaptured

• Mark and recapture informs estimates when the population moves.
• Organisms are caught and released back to be later identified.
• This is done to determine population size.
• The formula is (Amount 1st catch X total amount of 2nd catch)/Amount marked in 2nd catch = N.
• In this example, 52 deer are captured, marked and released back in the wild. After a week 21 deer are captured, and 12 of them have been marked.
• Calculating the deer population in the forest: (52 x 21)/12 = 91 deer

Mark & Recaptured Sample

• Estimate the population of creatures that exhibit movement using the (Amount 1st catch X total amount of 2nd catch)/Amount marked in 2nd catch = N formula.
• An ecologist wants to know how many bunnies live in a forest and captures 150 bunnies to mark and release. A week later, they captured 36, and 15 are marked.
• Estimate by calculating (150 x 36)/15 = 360 bunnies in the forest.
• Limitations include harm done that reduces survival, the learned behavior of animals to avoid capture (resulting in overestimation), and animals being trapped easier because of food reward (resulting in underestimation).

Population Density

• Density measures how tightly an object is packaged using Density = mass / volume calculations.
• Mass represents how much matter the object contains, while volume is how much space the object occupies.
• Population density describes individuals in a specific area.
• Mass equals population size, and volume equals area.
• To find the population density of Miami in 2023, divide its 2,687,568 people by its area of 1,898 sq mi for a total of 1,416 people sq mi.
• To determine the population density of Paris, divide its 2020 population of 13,064,617 by its area of 7,313 sq mi for a total of 1,787 people sq mi.

Species Distribution

• Species dispersion patterns reveal the spatial relationship between members of a population within a habitat at a specific point in time.
• Patterns include clumped (clustered), uniform (equally spaced), and random (no discernible pattern).
• Clumped groups of plants drop seeds nearby and some animals live grouped together.
• Allelopathy in plants inhibit growth of others nearby for a uniform distribution.
• Uniform populations occur when animals mark and defend defined territories.
• Random distributions are those with no patterns, such as plants with windborne pollen.
• Random distributions may cause problems finding a mate for solitary members.

Demography and Population Dynamics

• Population dynamics includes birth rate, death rate, and life expectancy.
• Birth rate (B) describes the individual births over a set period.
• Death rate (D) is the individual deaths over a set period.
• Life expectancy is the mean lifetime remaining to those that reach a certain age.
• The CDC calculates the average American life span to be 77.5 years, and this number is heavily determined by factors like such as race, sex and lifestyle.
• Mortality rate measures the number of deaths over a certain age, and this data is used in life tables.
• Teens have increased mortality, as the brain is not finished developing.

Population Growth

• Population growth rate (r) measures organisms added in each reproductive generation.
• Use the formula r = B - D to calculate population growth rate.
• If birth rates exceed death rates, populations increase.
• If death rates exceed birth rates, populations decrease.
• A population remains unchanged if r = 0.
• Density-independent (abiotic/non-living) factors of population growth include space, natural disasters, sunlight, temperature, water, and nutrients like nitrogen and phosphorus.
• Density-dependent (biotic) factors also affect population size, and work together with density-independent factors to regulate population size and growth.

Regulation of Density Dependent Populations

• Density-dependent limitations are biotic, and include Intraspecific/Conspecific and Interspecific/Heterospecific competition, food availability, waste accumulation, and disease.
• Intraspecific/Conspecific competition states that the most fit will have higher chances of survival, having more adaptions, which are beneficial traits.
• Interspecific/Heterospecific competition states that the most fit species has the higher chance of survival.
• Predation refers to whether predator or prey organism hunts another as a food source.
• An accumulation of of waste and disease lowers population size.
• Population growth rates are reduced with more intraspecific competition for food.
• High populations make it easier for diseases to spread.
• Low population densities cause difficulty finding a mate.
• More individuals provide genetic variation and the potential to adapt to the environment resulting a more stable population.

Exponential Growth

• Exponential growth accelerates the pattern of increasing population size.
• Exponential growth is represented by the formula x(t) = x(0) * (1 + r)^t.
• In this formula, x(0) stands for starting population, r stands for growth rate, and t stands for time.
• To show exponential growth, culture Staphylococcus aureus and account for binary fission every hour.
• A starting culture of 100 cells equals 800 in three hours.
• The exponential growth graph looks like a J-shape and doubles versus growing by a set amount.

Exponential Sample

• Find growth rate using the formula x(t) = x° (1 + r)^t
• Bacteria Escherichia coli reproduce through binary fission in 20 minutes, calculate the population after two hours starting from 150 with:
• 150*(1 + 1)^6 = 9,600 cells
• Exponential growth occurrs for small populations.
• Sustainable population is difficult to achieve in reality.

Logistic Growth

• Sustainability defines meeting present needs without compromising the future.
• A population that grows past a certain level results in fierce competition for resources such as space, water and food.
• Only the most fit individuals (natural selection) survive in a specific environment and carry down their adaptations with genes.
• Population growth follows an S-curve where exponential growth is present when the population is small/plentiful.
• As population growth increase the consumption, population growth rates decrease.
• Populations plateau once the consumption rates and resource replenishment rate is equal.

Long-Term Effects of Exponential Population Expansion

• The Principle of Population essay theorized that improvements (Industrial Revolution) would lead to population growth (Malthus, 1798).
• Rapid population growth would be unsustainable, as food production had limits.
• Limited food produce leads to a limited carrying capacity.
• Darwin used this to consider the Origin of Species in 1859.
• The Population Bomb essay warned reaching max population size would cause a rise in death rates (Ehrlich, 1968).
• Technology aids humans in increasing population carrying capacity.
• Some species become endangered due to over extraction.

Human Population Size

• Worldwide human population trends include:

  • 2004: 6.476 billion
  • 2014: 7.2 billion
  • 2024: 8.09 billion

• Human population size has a pattern of continually increasing.

• Abiotic and biotic factors affect population even though humans can alter the environment (Ex: Forest clearing).

• Long-term increased exponential population size carries death when not sustainable.

Human Ingenuity

• Humans alter the environment to increase carrying capacity by intelligence, society, and communication.
• As social animals, humans use language and writing to communicate ideas to the next generations to improve previous accomplishments.
• Construction provides shelter.
• The Neolithic (Agricultural) Revolution allowed settled agriculture.
• Oldest hominid fossils originated in Africa, but have migrated to almost all land.
• Public health (wash hands), sanitation (Black Death) and modern medicine (surgery) have decrease the effect of infectious diseases which limited growth.
• Transformation has harmed the environment and endangered the ecosystems.
• Human activities lead to erosion from acid and global climate change.

Developmental Stages

• The developmental stages include Prenatal Development, Infancy, Early Childhood, Middle Childhood/ Pre-teens, Adolescence/Teenagers, Early Adulthood, Middle Adulthood, Late Adulthood/Elderly/Seniors
• The prenatal phase includes first, second and trimester.
• Infancy consist of newborns (birth to 4 weeks), infants (5 weeks to 1 year), and Toddlers (1 - 2 years).
• Early Childhood occurrs from 2-6 years.
• Pre-teens / Middle Childhood happen between the age range of 6 – 12 .
• Teenage / Adolescence takes place from ages 12 – 19.
• Early, middle, and senior/late adulthood take place at ages 20 – 40, 40 – 65, 65+ accordingly.

How Populations Can Grow

• Keeping population constant to consider factors like sexual production, that requires 2 humans.
• To maintain equilibrium, two parents need two kids.
• Offspring production must meet survival needs, considering humans have tech/ability survival rate.
• 2.1 rate needed to maintain constant population levels.
• Age structure refers to population proportion at ranges.
• Population age identifies rates of reproduction cycles.

Rapid Population Growth

• Rapid growth is associated with high rates.
• The distribution population lies within reproduction age.
• The graph produces a j-curve due to exponential rates of of population growth.
• This type of growth is normally associated with countries undergoing development.
• Older people depend on resources in the growing industries.
• High amount of resources in productivity results chances of reproduction and survival.

Human Population Growth

• Slow growth in developed countries result in the same birth and death rates.
• The age distribution is at a steady range and a linear slope.
• Birth rates are relatively equal to death.
• This leads to zero population growth.

Declining Population

• A declining population, has the majority past the reproductive age.
• The graph generates reverse j-shape curve.
• Low rate of survival with not offspring to support in the future.
• Creates decline rate with developed countries .
• One country has enacted policy over population (one-child policy- China).

Life History

• Organisms need maintain homeostasis, reproduce and grow.
• Energy budget dictates how it is allocated.
• Body maintenance (growth/homeostasis).
• Fecundity, allows reproductive individuals within given range.
• Life history accounts the lifetime details for reproduction and maintenance.
• Traits can both be inherited and learned over the lifespan.

Body Maintenance & Reproduction

• Energy budgets impact maintenance.
• Growth rates promote predators of ecosystem.
• Can affect ability to survive for production.
• Reproduction occurs from early transfer.
• This results in affect due to growth.
• Environments determines species.
• A stable growing environment affects maintenance.

Parental Care & Fecundity

• Care correlates the energy to growing offspring.
• Measure accounts for produce.
• Care inversely relates to offspring.
• HIgh count reduces parental care.
• Fish results survival on count.
• Number with rate high.
• Rates of help and production.

Survivorship Curves

• Data is compiled of the species'.
• Low offset indicates high reproduction rates.
• Amount has occurs on mid rates.
• Occurs with death rate.