Ecosystems and Their Diversity

Ecosystems and Their Diversity

Introduction to Ecosystems

• The Alberta Badlands showcase a seemingly inhospitable environment that is, in reality, home to various species such as eagles, hawks, ground squirrels, rattlesnakes, scorpions, and resilient plants like cacti.
• The biodiversity in the Badlands differs from that of river valleys and northern Alberta spruce forests.
• Life isn't uniformly distributed on Earth due to abiotic factors.
• Organisms derive energy from sunlight (directly or indirectly).
• Each organism needs specific levels of abiotic conditions (temperature, humidity, salinity, and moisture).
• Organisms can only tolerate fluctuations within a certain range; there's an optimal level for each.
• Abiotic factors primarily dictate the distribution of Earth's organisms.

Climate and Biomes

• Climate represents the average weather conditions in a region over a long period (30+ years).
• Climate is determined by temperature and rainfall, which stem from unequal heating of the Earth, local geography, snow/ice cover, and proximity to large water bodies.
• Unequal heating causes major climate zones, from tropics to temperate zones to the cold regions near the poles. Figure 3.15 illustrates this, noting that sunlight strikes the equator more directly, while sunlight reaching the poles is spread over a wider area.
• The unequal heating creates global air and water movements which in turn interact with features like mountains and lakes to produce rainfall patterns. Some areas become dry, while others become wet.
• Precipitation patterns influence soil formation.
• The combination of precipitation, soil, topography, altitude, latitude, and temperature determines the types and abundance of photosynthetic organisms.
• Photosynthetic organisms, in turn, determine the variety and population sizes of other species (animals, fungi, etc.).
• Biomes are large ecosystems or groups of ecosystems in specific regions. They feature particular mixes of plants, animals, and other organisms adapted to specific environmental conditions.

Terrestrial Biomes and Abiotic Factors

• When terrestrial biomes are plotted by mean annual temperature and precipitation, distinctive patterns emerge (Figure 3.16).
• Generally, terrestrial life increases with temperature and precipitation. However, excessively high temperatures can limit this increase.
• The distribution of organisms directly relates to abiotic conditions in the biome.
• Changes in temperature vary with latitude and altitude (elevation).
• Mountains can affect precipitation, leading to variations in biomes. For example, grasslands can be found at the base of mountains instead of forests (Figure 3.17).
• Figure 3.18 displays the distribution of Earth’s terrestrial biomes by latitude.
• Each terrestrial biome is characterized by communities adapted to specific physical conditions.
• Aquatic biomes include lakes, rivers, estuaries, coral reefs, intertidal zones, open ocean, and deep sea.
• Transitions between biomes are gradual, not abrupt. Example: The taiga and tundra transition in northern Canada involves a gradual change in plant and animal composition.

Habitats and Ranges

• Biomes contain a variety of habitats.
• The taiga biome in central/northern Canada, Europe, and Asia demonstrates wide variation from north to south and east to west.
• Vegetation zones within a biome can be further classified (Figure 3.19 shows vegetation zones in Alberta).
• Habitats are places/areas with specific biotic and abiotic characteristics.
• Each species is found in a specific habitat where its adaptations allow it to survive and reproduce.
• A species' habitat can be a single large area or multiple separate locations.
• Example: Hoary marmots reside in alpine and subalpine areas of western Canadian mountains (Figure 3.20).
• The range of a population/species is its geographical area.
• A species’ range is limited by its habitat requirements.
• Environmental variables, including abiotic (temperature, rainfall) and biotic (food type) factors determine habitat.
• Hoary marmots don't live throughout their entire range, but only in suitable habitats within it (Figure 3.21).

Ecological Niche

• Different species can share a range or habitat due to varying ecological niches.
• An ecological niche is the role a species plays in a community and the total range of biotic/abiotic needs for survival.
• Example: The northern long-eared bat's niche involves its tolerated temperature range, roosting trees, and size/type of insects it consumes (Figure 3.22).
• A population's habitat is its "address," while its niche is its "job" in the community.
• Species can coexist in the same habitat with different niches by nesting in different trees or feeding on different insects.
• Problems occur when one species' niche impacts the habitat of others (e.g., mountain pine beetle infestations).

Habitats and Niches within Ecosystems

• Differing biotic/abiotic characteristics within an ecosystem result in diverse habitats and niches.
• Lakes have vertical stratification due to varying light and nutrients.
• Upper layers of a lake have sufficient light for photosynthesis, while deeper layers are colder.
• Each species occupies a niche required for its survival.
• Photosynthetic organisms inhabit warmer, brighter surface waters, as do their consumers.
• Other photosynthetic species need to be rooted in bottom sediments close to the shore.
• Animals swim or crawl along the bottom.
• Figure 3.23 depicts zones in a lake based on depth (light and temperature) and distance from shore (habitat for floaters, swimmers, and bottom-dwellers).
• Terrestrial communities exhibit similar habitat and niche diversity.
• Forests have soils with differing mineral and moisture content, supporting different plants, which then provide food/habitat for different animals.
• Biodiversity varies in different areas based on abiotic and biotic components.
• Figure 3.24 compares a harvested forest replanted with only one tree species (monoculture) to a mixed forest with greater species diversity.
• A monoculture has less diversity than a mixed forest.

Factors Limiting Growth in Ecosystems

• Trembling aspens are fast-growing but aren't found everywhere.
• Bacterial populations can't grow unlimitedly; otherwise, they would outweigh the Earth in a few days (Figure 3.26).
• 1.1 \times 10^{12} individuals would be created after 20 hours
• After four days, the bacterial population would outweigh Earth.
• Populations can't sustain unlimited growth.
• Limiting factors (abiotic and biotic conditions) control population size.

Abiotic Limiting Factors

• Abiotic components limit the distribution and size of populations.
• Plants have optimal abiotic requirements (soil type, moisture, humidity, temperature).
• Abiotic requirements control plant populations.
• Gardeners, farmers, and foresters consider abiotic factors.
• Changes in conditions compromise plant growth.
• Cottonwoods along the Oldman River are adapted to periodic flooding (Figure 3.27).
• Flooded conditions are critical for young seedling growth.
• Damming rivers changes water levels and flow, impacting cottonwood populations.

Biotic Limiting Factors

• Populations grow rapidly then level off (births ≈ deaths).
• Biotic factors like resource competition, predators, and parasites slow population growth.
• Competition limits population size based on resource availability.
• Intraspecific competition is competition within the same population for limited resources (food, water, sunlight, shelter, mates, breeding sites).
• Interspecific competition is competition between different populations for resources.
• One species may outcompete another, leading to the "losing" species disappearing. An example of this concept can be seen with bull trout being out-competed.
• Similar but not entirely overlapping niches allow species to coexist but may lower population densities.

Predators Limit Populations

• Predation is when one organism consumes another.
• Predators and prey have significant impacts on communities.
• Example: Arctic foxes introduced to the Aleutian Islands decimated native seabird populations (Figure 3.30).
• Seabird droppings (guano) fertilized the soil, allowing for grassland growth. With fewer birds, guano decreased, transforming grasslands to tundra.

Parasites Limit Populations

• Parasitism is when one organism benefits at the expense of another.
• Host isn't always permanently harmed or entirely consumed.
• Increased host density increases parasite numbers.
• Higher parasite numbers reduce the host's survival/reproduction.
• Fluctuations of parasite/host are similar to predator/prey cycles.

Sampling Populations in Ecosystems

• To determine population size, ecologists estimate rather than count every individual.
• They count/estimate the number of individuals in samples (small portions of the population) then calculate the average.
• The results are extrapolated to the entire area (Figure 3.31).

Estimating Numbers Using Transects or Quadrats

• Organisms are sampled along a transect (a long rectangle).
• A starting point and direction are randomly chosen, and a line of a certain length is marked out.
• The occurrence of any individual within a certain distance of the line is recorded (Figure 3.32).
• For plants: ecologists use quadrats to sample a population.
• Several locations are randomly chosen, and a quadrat of the same size is marked out.
• The number of individuals of a species within the quadrat is counted.
• Density is calculated by dividing the average number of individuals per quadrat by the size of the quadrat.
• Population size can be estimated by extrapolating from density to the entire study area.
• Random samples are important, meaning that all individuals have an equal chance of being represented.