Populations and Ecosystems
Concepts
population of plants can work together without interacting individually with each other.
population also does not exist in isolation ✅
an individual plant never exists in isolation in a habitat, other individuals of same species together form a population 👥
a combination of various populations create a community and multiple communities along with physical, nonliving things creates an ecosystem ⭐ ❤
ecology is the study of organisms in relations to all other aspects of their surroundings ⭐
populations are rarely stable, change is more common.
good when attracting pollinators
bad when spreading diseases
Plants in Relationship to Their Habitat
Abiotic Components of the Habitat 
Biotic Components of the Habitat
habitat is the set of conditions in which an organism completes its life cycle ✅
major problem presented is how much of an environment is considered part of a habitat ❓
can vary for different species e.g. migratory birds
aspects of the habitat that directly affect a plant constitute its operational habitat 🔬
all components essential and nonessential make up the plants habitat
abiotic habitat consists of nonliving physical phenomena including climate. soil, altitude etc. ❌
biotic habitat consists of living factors such as plants, animals, fungi, protists, and prokaryotes ✅
latitude and altitude
Disturbance
soil factors
climate
average temperature is not as important as its extremes, many plants cannot survive certain extremes 🌡
moisture such as rain and snow can supple water bud damage a plant, and in some climates be sparse or abundant year round ⛈
critically important to all organisms, can restrict organism growth and movement if not preferable to plant ❎
growing seasons of an area are controlled by the last severe killing frost in spring ❄
numerous metabolic processes respond to proportionally to abiotic factors
between low and high extremes is the tolerance range of an organism ✅
these vary greatly between species, from very broad to very specific ⚠
first plants that invade new soil are called pioneers and must suffer severe lack of nutrients and help soil become nutrient rich ❤
through time, thick soil can produce three distinct layers called horizons.
soil is formed by the breakdown of rock, lack essential macro-nutrients and micronutrients ⭐
young soils differ due to chemical nature of parent rock, thick soil is less diverse : ⭐
A horizon is uppermost and is sometimes called zone of leaching, consists of litter and debris, and washes downward with rainwater 🚩
B horizon or zone of deposition is area where materials from the A horizon accumulate, rich in nutrients and clay 🏴
C horizon the composed mostly of parent rock and rock fragments 🌕
altitude relates to amount of aboitic conditions as well such as wind and soil conditions ⛰ along with intense UV light
latitude contributes to abiotic factors such as sunlight amount and day lengths along ✅
will have direct impact on biotic factors but not abiotic factor in an ecosystem 🚩
fire is a major component of disturbance and has caused organisms to adapt accordingly to help survive better
disturbances are phenomena such as fires, landslides, and avalanches that produce radical change in ecosystem 🔥
many properties of fires can be beneficial afterwards such as nutrients from ash and mineral releasing once burnt in plants ♻
Other plant species
The plant itself
pine forests for example, their seeds need sunlight to grow but will not receive it due to shade by older trees, only disturbances can clear pine forest for their seeds to grow
pioneer plants can help enrich soil in glacier retreats but can be out competed by secondary plants who shade the area ⛔
an individual in a habitat modifies the habitat and is a part of it and habitat modification can be good, bad, or neutral to plant ✅
geographic ranges of most populations are extensive enough to include a diverse group of biotic and abiotic factors
when several individuals of one or several species occur together, chances of interactions occur ✅
Organisms other than plants
if both parties are at a disadvantage, then it is competition ❌
if both countries benefit, then it is called mutualism 😃
competitive exclusion occurs when the less adapted species is excluded from the ecosystem by superior competitors 🚫
niche occurs when a resource is used effectively by one species and not by another, selective conditions ✅
occur when two populations grow better individually than together and creates a competition for resources 🚩
refers to how an aspect of a habitat can affect a species
another theory states that species can overlap in tolerance ranges and have an exclusive use of a portion of resources ⭐
to test ecotypes, transparent experiments are performed which plants are growing in an alternative area in a common garden
animal life and abiotic factors in a region can also affect competition between two plants ⭐
ecotypes occur as a specialized response to particular ecosystem factors at its locality. 🏁
commensal relationships occur when one species enefits and the other is unaffected ♻
Predation is a relationship in which one benefits and the other is harmed ☠
plants and other organisms can have a mutalistic relationship such as a bird germinating and spreading seeds of the fruit it ate ❤
animals that only eat plants are herbivores and the process is herbivory ✅
relationships between plants and fungi are described as pathogenic rather than predatory ⚠
examples of plant fungi mutalism include mycorrhizal fungus transporting phosphate into the plant and in turn receive carbohydrates ⭐
browsing (twigs, leaves and shrugs)
grazing (eating herbs)
The Structure of Populations
Age Distribution: Demography
r and K selection
Geographic Distribution
Local Geographic distribution
Boundaries of the Geographic Range
a factor that determines the health of a plant is known as the limiting factor ⭐
biotic factors are also critical. ⚠
the ability of a plant to spread throughout a geographic area is a result of its adaptations to the abiotic and biotic components ✅
soil factors also produce geographic boundaries for most populations of plants ⛔
applies to all aspects of the plants interaction with its environment
if plants receives sufficient amount of this factor then it will grow until a new limiting factor is presented 🚩
can be any factor from the ecosystem
desert plants cannot compete with other plants if presented into a new moist environment
animals and their migrations also act as limiting agent if plant population is not able to move throughout geographic region 🏁
can be due to mineral composition and texture : ✅
random distribution is used when there is no obvious pattern to positions of individuals and has no predictive value ✅
clumped distribution are those in which the spacing between plants is either small or large, but rarely average 🏴
small scale, local distribution of individuals in respect to each other is also important ⭐
can be result of seeds falling close to parent plant, or animals that eat fruit deposit them in localized area
Uniform distribution are the types that occur in orchards and tree plantations 🍎
not very common in nature
some plants produce a chemical called allelochemics which inhibit growth of another plant 🚫
inhibition is called allelopathy ⭐
two factors affect the possible rate of population growth
biotic potential is measured under ideal conditions but this rarely occurs in nature 🏴
the manner in which a population responds to various factors is affected partly by its age distribution, ⭐
demography- the relative proportions of young, middle-age, and old individuals
mostly applied to animals, difficult for plants
generation time is the length of time from the birth of an individual to the birth of its offspring 🏴
intrinsic rate of natural increase or biotic potential is the number of offspring produced by an individual that can reproduce under ideal conditions ⭐
biotic potential will not equal the number of seeds produced
for many species, biotic potential is a large number represented in population equations r ❎
plants that produce large amounts of viable seeds have large r potential and potentially increase each generation ❤
the opposite is true for plants with low seed viability production
a population will increase in its number of individuals until it becomes to close to carrying capacity ⭐
the number of individuals in each population that can live in a particular ecosystem is limited, number is called carrying capacity ⚠
will create overcrowding and competition resulting in poor growth and lower reproduction 🚫
When N and K are equal death rates and birth rates are equal
many factors can attribute to an increase or decrease in birth rate and death rate
these factors can be due to pathogenic, predatory individuals causing stress on the habitat ✅
as a young population grows, biotic potential r is the only limiting factor given there is an abundance of resources ✅
eventually it will run into K, carrying capacity, and this will have the greatest continuing factor to population growth
r-Selection
K-Selection
pioneer plants will have the advantage as many of their seeds will find suitable sites for growth ⭐
biotic potential is the limiting factor for pioneer plants to to low predation and pathogenic spread through a population
a disturbance usually produces r conditions
r- Selected species typically are annuals or small shurbby perennials because disturbed habitat gradually changes 🏴
as more species and fungi become reestablished, r-selected plants become disadvantaged ⛔
disturbances are only way r-selected plants have a chance among the population and disturbances are unpredictable ❗
in a K habitat almost every possible site is filled.
is advantageous to live longer but costs lots of energy and resources.
conditions in a crowded habitat where a population is close to its carrying capacity, select for phenotypes very different from those that are beneficial in a disturbed habitat ⭐
K-selected species include many conifers and face competition for scarce resources ✅
can occur next to r selected plants
The structure of ecosystems
physiognomic structure
temporal structure
Species Composition
Trophic Levels
trees, shrubs, and herbs are the three most useful categories but in addition a system of life forms was created ❗
criterion for classification was means by which plant survived stressful seasons
physical size and shape of the organism, distribution in relation to others and environment is the physiognomic structure ⭐
an infinite : combination of possibilities of life forms as well as infinite number of ecosystems possible but only few exist 🏁
plants change dramatically with the season ⚡
late summer early autumn bring changes that depend on the ecosystem ⚠
changes that an ecosystem undergoes with time constitute its temporal structure ✅
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can be as short as a day or encompass seasons or decades ⏰
plants that bloom early spring will likely produce fruit during summer 🌞
species that flower late will release seeds in late summer or autumn 🍂
flowers and plants can bloom depending on seasonal conditions that are ideal for growth
depends on climate soil composition and species tolerance ranges being wither broad or narrow
competition is intense but natural selection has resulted in habitat partitioning with each species occupying a narrow portion of various resource gradients ✅
species composition refers to the number and diversity of species that coexists in and ecosystem : ✅
presence of a large number of species actually creates more niches that can be filled by a species ⭐
Autotrophs are known as primary producers and they are the first step of any food web as they produce their own food by photosynthesis ⭐
the transfer of energy in an ecosystem is usually displayed by energy flow or the carbon flow of the ecosystem
are basically feeding levels which display energy transfer through various animals in an ecosystem ❤
give way to primary consumers who are herbivors that eat the primary producers and consuming their energy ⚡
primary producers are then consumed by secondary consumers consisting of carnivores and omnivores ⚡
secondary consumers eventually die and are consumed by decomposers that break down whats left of the animal ✅
CO2 is released back into the atmosphere and then later used again in photosynthesis all over again
minerals also flow through the ecosystem. ✅
each step results in ATP heat, CO2 and water production ♻
once organisms die the minerals released by the dead orgainisms is transferred back to the soil to be used again
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minerals are absorbed by the plant through the soil and then transferred through each trophic layer in consumption 🚩
movement of energy and biomass from trophic layers is represented by a pyramid of energy ⚡
can show how harmful chemicals will not go away but accumulate in the bodies of animals 💥
pyramid is important in displaying affects of human introductions of things such as herbicide ⭐
decomposers are vital to the trophic system
affect plant growth as if no decomposers present, growth and nutrients depend on the degradation of rocks ⏲
break down dead materials and release nutrients back into ecosystem ✅