Ecology: Communities, Populations, and Ecosystems

Ecology Essentials

• Adaptations, interdependence, and competition are key ecological concepts.

Community

• Groups of different species populations, encompassing animals, plants, protoctisa, fungi, bacteria, and archaea, that are all interdependent and live in a shared habitat.
• Species within a community rely on each other; for example, plants create food via sunlight and photosynthesis that animals consume.
• Animals may pollinate plants, consume other animals, or utilize plant and animal matter for shelter.
• Plants benefit from nutrients in animal waste and decomposition.

Interdependence

• One species affects the entire community.

Population

• All individuals of a single species within a specific habitat at a given time.
• Populations do not exist in isolation and can coexist within communities.

Ecosystem

• A community of organisms interacting with non-living (abiotic) environmental elements.
• An ocean ecosystem includes fish (living) and water temperature (non-living).
• Photosynthesis depends on sunlight and also factors like temperature, soil pH, and water levels.
• Predator-prey relationships, pathogens, and pests create biotic ecosystem elements.
• Ecosystems consist of complex communities where species depend on each other and adapt to their environment.

Energy Source

• The sun transfers energy through ecosystems via chemical bonds within organisms.

Material Recycling

• Non-living elements (carbon, nitrogen, water) are recycled.
• Microorganisms play a key role in processes like the carbon, water, and nitrogen cycles.

Abiotic Factors

• Non-living factors impacting population size: temperature, light, pollution, and soil pH.

Biotic Factors

• Living factors affecting population size: new predators and diseases.

Stable Communities

• Environmental factors in stable communities are relatively constant but can change, for example with UK seasons.
• Species and population sizes in stable environments remain balanced.
• Tropical rainforests, ancient oak woodlands, and mature coral reefs are significant stable communities with a wide range of species.
• A single mature oak tree can support 1000 other species.
• Communities have limits to change tolerance, that can lead to deforestation, for example.

Organism Survival

• Organisms must adapt to their environment for survival and breeding.
• Reindeer thrive in cold environments with limited plant growth due to low light and temperature, travelling long distances for food and protection.
• Plants require light, water, minerals, and space.
• Animals need food, mates, and territory.

Population Size Factors

• Biotic and abiotic factors influence population size.

Biotic Factors Examples

• Increased food leads to successful breeding, while scarcity causes struggle.
• New pathogens or parasites can devastate populations due to lack of organism resistance.
• New predators introduced can cause organisms to die quickly where there is no defence.
• New arrivals may outcompete existing species, reducing numbers and breeding rates, with grey squirrels outcompeting native red squirrels as an example.

Interspecific Competition

• (competition between species) and organisms like animals, plants, fungi, protista, bacteria and archaea struggle for resources like their community.
• Success in competition affects survival, reproduction, and death.

Abiotic Factors Examples

• Light intensity: Affects photosynthesis & distribution of plants, with some adapting to low light with larger leaves and more chlorophyll.
• Temperature: High temperatures denature enzymes and limits photosynthesis.

Temperature And Plants

• In cold climates temperatures limit photosynthesis.
• Lower temperatures in arctic regions limit the size of plants.
• Moisture: Water is a reactant in photosynthesis, lack of water restricts life.
• Soil pH and mineral content impact plant distribution.

Mineral Levels

• Carnivorous plants thrive in low nitrate environments because the protein provides the required nitrates.
• The pH of soil affects decay rate and mineral ion release.
• Low pH inhibits decay and nutrient cycling.
• Some invertebrates survive with low levels of O2, but most fish need high levels of dissolved O2.
• CO2 levels can affect photosynthesis and plant growth.

Wind

• Wind intensity affects the transpiration rate.

Factor Interactions

• Abiotic factors interact to create unique environments for species.

Predator-Prey Cycle

• Linked to Interdependence

Cycle Phases

• Predators eat the prey decreases their numbers significantly
• Increased prey allows predators to increase.
• Predator decrease when there's not enough prey and allows prey numbers to recover.

Population Measurement

• Abundance - the # of living organisms that live in a specific habitat.
• Distribution is where the organisms are found.

Systematic Sampling

• A transect line in a changing habitat is used (beach to dunes).
• Quadrats are placed along the line to count organisms and determine percentage cover.
• Repeat along transects.

Random Sampling

• Random co-ordinates are used with the quadrat.
• Data is collected as percentage cover.

Quadrat

• The method to count the number of organisms e.g. plants.
• Can be used for slow moving animals like snails.
• They are of equal size and there are as many samples as possible.
• Sample areas selected at random to reflect the true distribution. A person can close their eyes, spin around etc
• You need to take several random readings and then find the mean number of organisms per m2. This technique is known as quantitative sampling. You can use quantitative sampling to compare the distribution of the same organisms in different habitats. You can also use it to compare the variety of organisms in several different habitats.

Systematic Sampling

• Used to measure effect of abiotic factors on distribution.
• Measuring the distribution of organisms along a transect, a line transect is most commonly used.
• You stretch a tape between two points, for example a rocky shore, across a pathway or down a hillside. You sample the organisms along that line at regular intervals using a quadrat + shows you how the distribution of organisms changes along that line.
• Measure light and soil, which affect plants.

Competition

• The best adapted organisms win competition for resources and outcompete the others.
• The best characteristics will outcompete the others, survive and reproduce and passing on their genes for the most successful characteristic to the next generation.

Animals And Plants Compete

• Animals compete for food.
• Plants compete for space, light, and water.
• Light is needed for photosynthesis to make food.
• Trees take up water, nutrients and light from soil.
• Some desert plants produce a chemical that stops seeds from germinating, killing the competition before it even begins to grow.
• Therefore it is important for plants to disperse their seed as far away as possible from themselves e.g., wind dispersal→ the wind carries the pollen away, insect dispersal→ insect e.g., bee carries the seed away.

Plant Adaptions

• They avoid competition by not growing close to each other, by having different types of roots, and growing to have a leaf with a large surface area to absorb as much sunlight as possible.
• Plants in woodlands flower early in the year.
• Dormant trees take up very little water.
• Shed leaves from previous autumn rotted down to provide the mineral ions in the soil.
• Other plants have shallow roots taking water and nutrients from near the surface of the soil, while other plants have long, deep roots that go far underground.
• Tendrils and suckers adapt so they can climb.

Animals And Plants

• With animals as with plants there is the within species and other species to compete with.
• They also reduce the amount of light reaching the plant beneath them. The plants around them need adaptations to help them survive.
• Some animals contain poisons that make anything that eat them sick and have warnings to avoid predators.

Territories And Mates

• Lions compete with each other for space and territory, intraspecific, lions competing with hyenas, interspecific animals setting up and defending a territory is vital.
• If they have no territory they will compete for the best spaces, this makes sure they will be able to find enough food themselves and for their young. The # of territories found in the area varies with the amount of food available and they use urine or faeces to mark the boundaries of their territories.
• For mate, male birds have mating songs to compete with each other for female birds and in many species, the male animals put a lot of effort into impressing the females which they compete in different ways to win.

Survivial

• Only successful competitors will survive through natural selections, especially when the environment changes because they will be able to breed and pass on their allele for a favorable characteristics to the next generation.
• It is also important that they avoid competition with other species as much as possible. Some do that in a way that no other local animals do, like feeding on one plant without direct competition.

Natural Selection Survival

• Those that are better adapted will outcompete others for food, mate and territory.
• Those that survive / breed will produce offspring with the same advantageous characteristics, so the number of individuals with advantageous the characteristics in the population increases and those that don't have this decrease.
• Adaptation is when plants need to adapt to obtain light, CO2, water, O2, and mineral ions to produce glucose.

Animals

• compete for food (prey), mate, territory. Therefore they have the adaptations to obtain this. In addition they also have to survive in their habitat from predators. Microorganisms: best adaptations.

Animals And Plants: Different Atmospheres

• Polar bear (Arctic) has a thick fur insulator that reduces thermal energy being transferred to the surroundings;
• Fur white that acts as camouflage (they become less visible to their prey); underneath the fur, they have black skin (best at absorbing heat, poor emitters (to release.
• Camel has long eye lashes, and a tough tongue.
• The plants have leaf that has a large surface area to absorb as much light as possible and are thin and palisade cells that are packed with chloroplasts. The root adapts to absorb more water because the cell has extensions that provide an increased surface that can be absorbed from the soil by osmosis.
• Plants can reproduce rapidly by asexual reproduction because they only need one parent and this gives them a better success chance.
• A Retain water in areas where there is low water availability e.g., cactus, has no leaves, but contains thorns/spikes to prevent herbivores that allows it top retain the water in their tissue.
• They also include Sunken Stomata sunken into pits, helps to reduce the water concentration gradient.
• Extremophiles live in the most difficult conditions e.g., thermophilic bacteria, are adapted to live near volcanic vents where the temperatures can be very high but some have also adapted to live in salty conditions, acidic conditions, without O2.
• These organisms are bacteria called thermophilic bacteria that live near volcanic vents with a temperature range of 45-80°C or higher and have enzymes that do not denature at these temperatures.
• Some survive in very salty environments (bacteria have adaptations to their cytoplasm so that water does not move out of their cells and could swell and burst).

Hot And Cold

• Cold climates have to survive and stay warm surface to volume is very important to reduce the transfer of energy to the environment, to reduce cooling this is why artic animals are large. They also have thick skin and blubber.
• Animal camouflage is important; arctic animals adapt.
• They must also adapt to survive to in dry climates;
• They can adapted or have functional adaptation.

Plant Adaptation

• The plants adapt to hot and dry conditions, reducing the water loss.
• Some examples of plants with specialised adaptations are:
• i) Marram grass grows on sand dunes has tightly curled leaves to reduce surface area for so it can survive dry conditions.
• The best known have cacti leaves/ spines that deter eating.

Collecting And Storing Data

• Extensive root conditions that spread over a wide.
• They Store water after rain .

Survival And Evolution

• Explain how several different species of camel could have evolved from a common ancestor over 45 million years:
• There is isolation of separate camel populations by sea/mountains along with a variation in habitat. There are biotic (e.g. food / predators) or abiotic, genetic variation/mutation and then 45 million years is sufficient time to accumulate enough mutations, natural selection, and better adapted survive to reproduce.