BIOEE 1610 Week 4

For homeostasis to occur, the heat input and heat output must balance each other out.

• Changing behaviour
• Color
• Insulation (layer with low thermal conductivity)
• Smaller leaves (higher wind speed on the boundary levels of the leaf, leading to higher convection)
• Smaller surface area is preferred in deserts. Another preventive strategy is to make the surface body more likely to reflect / absorb incoming radiation. Some adaptations are more complicated because of competing functions. Example: Polar bears. Although one might expect the bear to have black fur to absorb solar radiation, this color would make them a much less effective predator in the white environment. Thus, despite having white fur, polar bears have black skin. Additionally, animals may forage at night and sit out the sun.

Basal metabolic rate is calculated by using mass. Lower mass leads to less heat generated by metabolism.

It is the reflection of heat. (such as rocks on hot days) Living organisms have higher emissivities than most inanimate materials.

Heat exchange between ground and organism. (direct contact) Surface area making contact with the ground, the conductivity of the ground, and the temperature difference between the organism and the ground.

Heat exchange between air / water and organism. Depends on wind / water speed, temperature difference and surface area of organism.

Soguk kanli ve sicak kanli. Ectotherm’s body temperature depends on external environment, whereas the body temperature of endotherms depend mostly on internally generated metabolic heat.

Poikilotherms are organisms whose body temperature fluctuate. Ectotherms tend to be poikilotherms. Homeotherms are organisms with constant and stable body temperatures. Heterothermy are organisms that maintain a constant body temperature but sometimes allow it to fluctuate (such as animals who hibernate).

Through the latent heat lost through water evaporation.

Balance between input (absorption, ingestion, metabolic water) and output (secretion, transpiration / evaporation) of water.

• Freshwater: water intake through osmosis
• Saltwater: water loss through osmosis

Metabolism of food.

Organisms either maximize their water intake or minimize their water output (concentrated secretions, avoidance of evaporative loss through less stomata). Trade-off for water adaptations would be to choose between maintaining heat and maintaining water (water loss results in heat loss). It’s easier to heat a body than cool it down, as heating doesn’t require water loss. A similar trade-off is seen in photosynthesis in plants.

Maintaining constant body temperature allowed for mammals to forage at night. (nocturnal / btw diurnal is the exact opposite of that) Most mammals have a body temperature just above average daytime temperatures in order to be active at night.

0.03 x Mass^0.7

Energy and biomass decrease along the food chain due to loss to heat.

• More complex systems
• hunting , moving
• Complex reproduction
• Maintaining body temperature

• The entire organism is not consumed, so will be left to decay or will be excreted.
• Some organisms die without being consumed by the next trophic level.
• Cellular respiration, movement and warm blooded animals maintaining body temperature results in considerable heat loss.

• NPP (however, ecosystems with similar npp may have very different secondary production)
• Efficiency of energy transfers (second law of thermodynamics states that energy must always go to a more dispersed state after being transferred, deeming transfers very inefficient.)
• Food quality (ecological stoichiometry, low C:P and C:N ratios)
• Production efficiencies of consumers

• Consumption efficiency
• Assimilation efficiency
• Production efficiency
• The culmination of all 4 is called the trophic efficiency of the organism.

Describes how efficiently an organism feeds. Ingestion/Plant growth

• Describes how efficiently an animal assimilates ingested food into energy. (assimilated/ingested)
• Assimilation = ingested - egested

• Describes how efficiently an organism grows with the energy it assimilates. (production/assimilation)
• Production = assimilation - respiration

Production of consumer / production of plants

How key nutrients in the food, C, P and N, compared with the needs of the animal eating it. When the C:N and C:P ratios in the foods are most similar to the same ratios in the tissues of the mammal, the food seems to have a higher production rate according to the principles of ecological stoichiometry. Based on this, herbivores are expected to grow well on plants with low C:N and C:P ratios.

Ectothermic animals have higher production efficiencies than endothermic animals. A reason for this is that body temperature regulation takes away from the energy that could be used for production (growing).

An animal’s metabolic rate as it’s in the wild. The difference from basal metabolic rate is that the animal is free moving. According to research, ectotherms have a lower field metabolic rate than endotherms. Additionally, larger animals have higher efficiency due to surface area.

• It affects:
• The number of trophic levels
• Biomass distribution between trophic levels
• Relative importance of grazing and detrital food chains

A position in the food chain as determined by the number of energy transfer steps from autotrophs or detritus.

Heterotrophic, Photosynthetic, Chemosynthetic equally. They draw on a greater variety of energy sources than any other group of organisms.

Heterotrophic and photosynthetic equally.

Plants are generally photosynthetic, with rare occurrences of heterotrophy in carnivorous plants.

They can only be heterotrophic. However, an interesting example would be the eastern emerald elysia, which accumulates the chlorophyll from the algae it ingests on its upper back.

• Quality of food
• Consumer physiology

• Type of metabolism: endotherms < ectotherms
• Size of organism: small < big
• Food quality: bark < butter
• Energy spent getting food: high < low

• Rapid movement between warm and cool places.
• Modifying posture to alter body surface exposure to sources or sinks of heat.
• Regulation of time of day when active.

Maintenance of constant, relatively high body temperature by having a large body and insulation.

As body size increases SA/V decreases and approaches 0.

According to Bermann’s Rule, as latitude increases (moves closer to the poles and temperature decreases), the size of the animals increases. The reason for this is that lower SA/V ratio ensures higher conservation of heat. In warmer areas, smaller size, longer limbs and longer ears allow for heat dispersion.

SA/V is connected to animal diversity, their strategies across biomes and food consumption.

• Food and space resources
• Inter-specific and intra-specific competition / interactions
• Weather conditions

• Population ecology is the study of population dynamics such as:
• Population growth
• Dispersal
• Demography
• Distribution

• It’s useful for:
• Conservation efforts
• Monitoring pest species
• Measuring agricultural yields

• Simplify complex systems
• Predict the future
• Compare different systems

It grows exponentially ( or geometrically) (J curve) or logistically (S curve) based on the reproduction method of the species. (R or K strategist - remember r strategists are bacteria while k strategists are expensive species)

It is the growth of a population with non overlapping generations (discrete reproduction) and unlimited resources (no predation, disease etc.). For instance, species such as elk may experience geometric growth when they emigrate to a new place for a few weeks. Plants such as waterhemp, which produce once every year, also leads to a distinct reproductive cycle.

It is the factor by which the population multiplies over time in the case of geometric growth.

It is the ratio of the size of the population at one time over the size of the population at a previous time. Lambda = nt+1/nt for populations growing with geometric growth curve. If lambda is above 1, population is increasing. If it’s below 1, it’s decreasing. You can calculate future population size by multiplying the current population size by lambda.

In reality, the curves look more like an S, as resources are depleted and biotic factors such as predation and disease begin to take hold. This is called a logistic growth curve.

The maximum number of individuals an environment can sustainably support. When a population reaches carrying capacity, it begins to fluctuate.

• dN/dT = rN (1-N/K)
• K being the carrying capacity and N being population size.
• You can see from here that when K = N, the delta of population size will equal 0.
• dN/dT is the instantaneous population growth rate.

dN/dT/N It is the highest when the population is the smallest.

The proportion of the effect of density dependent factors on the population changes with population size (food, light, space, disease, competition, predation, parasitism), whereas the proportion of the effect of density independent factors doesn’t (thunderstorms, pollution, natural disasters) Density dependent factors can have long-term, carrying capacity changing consequences, whereas density independent factors are relatively short-term and don’t affect the carrying capacity of the environment.

Number of individuals of a given species in a given time in a given area.

• Understanding how and why population sizes change gives insight into the ecological world.
• Population size/ distribution is important for conservation efforts and management.

• Complete / total counts: may take long and is generally impractical.
• Capture / release: might be hard for larger animals that are harder to capture.
• Incomplete Counts: sample a part of the area and extrapolate
• Indirect counts: visual, auditory counts such as fecal pellets. This is more useful for comparative analysis.

We generalize important factors (birth, death, immigration, emigration) and ignore random factors.

We only take death and birth into account.

• Number of offspring produced per individual in population.
• Birth / population size

• Number of deaths per individual in population.
• Death / population size

• Per capita intrinsic rate of increase
• R = b -d
• When growth is exponential, r is at maximum (rm)

Lambda = 1+(birth rate - death rate)

Nt+1 = lambda * Nt

• Exponential population growth has continuous reproduction.
• Geometric population growth has distinct reproductive cycles.

Nt+1 = N*e^(r*t)

It assumes that there are no limits to population growth,

In the beginning.

In the middle.

Increases until K/2 and then decreases.

• The highest amount of yield that can be obtained from a population each year without diminishing its ability for full replenishment.
• Above MSY: unsustainable, damages the resource
• Below MSY: waste of resource

• Fixed quota: same number of [whatever] harvested every year.
• Fixed effort: variable % of population harvested

• Failure to implement MSY strategy in order to maximize income. Illegal fishing above MSY.
• Incomplete data on population size, growth.
• Environmental variability affecting K and r
• Politics: pressure from fisheries
• Lack of recognition of interactions among species (one species affecting the other leading to fishery crashes)
• Physical damage to the ecosystem due to fishing practices.