Living Earth - Ecology

Species

A group of organisms that can interbreed and produce fertile offspring.

Types of species classification

Morphological species concept

Phylogenetic species concept

Biological species concept

Morphologicsl species concept

Focuses on morphological similarities to define and seperate species. Easiest initial means of identifying species, yet can be subjective.

Phylogenetic species concept

Focus on smallest group of individuals sharing a common ancestor. Biologists trace genetic history by comparing traits, then deciding at what level of difference two groups can be defined as a seperate species.

Biological species concept

Focuses on group of population whose members can interbreed and reproduce with themselves, but not other groups. This means formation of a new species would require reproductive isolation, The existence of some barriers can prevent two members of two species from interbreeding and producing viable, fertile offspring. These include behavioural isolation, habitat isolation, and mechanical isolation. 

Biological classification

Classifying all living things on how closely related to each other they are. First created by Carl Linneaus.

What is the order of biological classification

The Tree of Life

Prokaryotic Cells

Single-celled organisms that lack a nucleus and other membrane-bound organelles. They include bacteria and archaea, and their genetic material is typically organized in a single circular chromosome.

Eukaryotic Cells

complex cells that contain a nucleus and other membrane-bound organelles. Unlike prokaryotic cells, their genetic material is organized into linear chromosomes and is housed within the nucleus.

Differences between Prokaryotic and Eukaryotic cells

Evolution

The change in the genetic composition of a population from generation to generation.

Genes

Discrete units of hereditary information that consist of nucleotide sequences of DNA. They have alternate forms, called alleles,

Homozygous

Two identical alleles

Heterozygous

Two different alleles

Genotype

The genetic makeup, or set of alleles, of an organism.

Population

All indiciduals of given species that live within the bounds of a given area.

Microevolution

Evolution on the smallest scale; population.

What mechanisms drive evolution?

. Natural selection - A process where individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals due to those traits.

. Genetic Drift - A process where chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.

. The Founder Effect - When a few individuals become isolated from a larger population, the smaller group may establish a new population, whose gene pool differs from the source population.

. Bottleneck effect: Sudden change in environment, reducing population size drastically.

. Gene Flow - Transfer of alleles in or out of a population due ti movement of fertile individuals or gametes.

Mutation

A change in nucleotide sequence of an organisms DNA or RNA of a virus

Macro-evolution

Evolution at and above species level. The splitting of one species into different species over longer time periods.

Allopatric speciation

When geographic barriers seperate an original population, leading to reproductive isolation of two sub-populations with no gene flow between them

Sympatric speciation

When two populatios become reproductively seperated despite geographic proximity. Often due to habitat differentiation, sexual selection, and polyploidy.

Adaptive radiation

A period of evolutionary change where groups of organisms form many new species, whose adaptations allow them to fill different ecological roles in communities.

Consequence of Mass Extinctions

They can aid adaptive radiation and ecosystem management (e.g. diversification of mammals after extinction of dinosaurs during end-cretaceous extinction.)

Physical properties of island that determine species diversity

. Size of island

. Distance of island to nearest mainland

Extinction

The death of a last remaining individual of a given species.

Mass extinction

A significant increase in species extinction rates compared to originatiion rates of new species.

Species-Area Relationship

Foundational concept in ecology; the number of species in an ecosystem increases with habitat size.

Alpha Diversity

Number of species at a particular site (Local Species Pool

Beta Diversity

The change in species composition between two sites

Gamma diversity

Number of species in entire landscape (Regional Species Pool)

Formula for Gamma Diversity

𝛾 = α * β 

Community Ecology

Which species are present, how each grows and reproduces, and what they do to each other (Species-centric)

Ecosystem Ecology

How life processes and cycles nutrients, water, and energy through the system. (Physical-centric)

Symbiosis

Different species of animal/plants living together, having positive or negative effects.

Symbiosis Diagram

Biosphere

The biologically active parts of the lithosphere, atmosphere, and hydrosphere

Biomes

Major life zones, characterised by particular vegetation types and controlled by temperature and water.

Autotrophic

A species making its own food, e.g. plants making food from sunlight through photosynthesis.

Heterotrophic

A species getting food from others, e.g. Animals eating other animals.

Photosynthesis equation

6CO2 + 6H2O → (C6H12O6) + 6O2

What does respiration transfer energy into? (Hint: ATP)

Adenosine Triphosphate. Captures solar energy to power the subsequent Calvin cycle (light-independent reactions), converting into carbohydrates.

How is the rate of photosynthesis controlled?

. Light

. Moisture

. Temperature

. CO2 concentration in atmosphere

. Amount of open stomata

Stomata

Thousands of pores on surface of leaves. Carbon dioxide diffuse in stomata. Plants have ability to open and close it.

Key parts of stomata

. Guard cell

. Stomatal pore

. Epidermal cell

Photo meaning in photosynthesis and Synthesis meaning in photosynthesis

Photo = Light reactions

Synthesis = Dark reactions

What happens in light reactions?

. Plants convert energy from sunlight into chemical energy.

. Light reactions produce ATP and NADPH, which are then used to fix carbon dioxide in dark reactions.

What happens in dark reactions?

. Dark reactions use energy produced by light reactions to fix CO2 and generate sugars.

. Done via the ‘Calvin Cycle,’

What is the photosynthetic maximum light wavelength for photosynthesis to occur?

Between 430NM and 660NM.

Types of photosynthesis

C3 Photosynthesis: Most plants

C4 Photosynthesis: Some tropical grasses

CAM Photosynthesis: Cacti and other dry tropical plants

Advantage of C4 plants

They use water more effectively than C3 plants, so have an advantage during droughts.

Despite this, when CO2 is abundant water use becomes less important so C4 plants lose their advantage at higher concentrations.

Niche

The sum of a species’ use of the biotic and abiotic resources in its environment. Similar species can inhabit the same environment but never the same niche.

Realized Niche

The overlap between niche and environmental space, showing where animals or plants can live.

Resource partitioning

The differentiation of niches that enable similar species to coexist in a community.

Type I Species

Inital low death rates, then steep drop as death rates increase among older age groups. Common among larger mammals that produce few offspring.

Type II Species

Constant deatn rate during organisms lifespan. Common along small mammals such as rodents and many invertebrates, lizards and plants.

Type III Species

Very high death rates, with inital sharp drop in early life reflecting very high death rates for the young, flattens out for few individuals that do survive. Associated with organisms that produce many offspring but provide little or no care, such as long-lived plants, fish, and marine invertebrates.

K-selected species

Selection for slower rates of population increase. (K = carryinf capacity of population). Advantage in stable environments.

R-related species

Selection for high population growth rates (r refers to intrinsic rate of increase of a population) - Advantage in unstable environments.

Population growth equation

dN/dt = rN 

Carrying capacity

The maximum number of individuals that can be supported based on available resources in a particular area.

Trophic levels

The different levels of consumption in a food chain.

Bioaccumulation

Where a nutrient, metal, or other compound accumulates as it moves up through trophic levels.

Disturbance

An event that changes a community by removing organisms from it or altering resource availability.

Succession

Non-seasonal, directional and continuous pattern of colonisation and subsequent change in abundance at a site by species populations. Often triggered by a major local disturbamce.

Primary succession

No remnant of a previous community exists, e.g. new sand dunes, lava flows and land exposed by glacial recession. Timescale = tens to hundreds of years. 

Secondary succession

Resources remain. E.g. tree falls but well-developed soil and seeds remain; river disturbed by a severe flood, post-fire. 

Sere

The name of each stage of succession.

Facilitation

Early successional species alter the availability of resources, making it more suitable for other late successional species.

Logistic growth/ S curve

a population growth pattern where rapid expansion (exponential growth) slows down and stabilizes as the population hits the environment's limit, forming an "S-shaped" curve. It occurs when resources become limited, causing the population to level off at its carrying capacity (K)

How much more moisture does a warmer atmosphere hold?

7% more moisture per 1c of warming.

Physiology

The metabolic functioning of animals and plants. Examples include respiration, photosynthesis, development etc. 

Physiological effects of CO2

. Stimulation of photosynthesis 

. Increase water use efficiency 

. Increase biomass production 

Which type of plant becomes more efficient at higher CO2 concentration?

C3 Plants

Phenology

The study of periodic events in life cycles and how they are influenced by climate. Examples include flowering times, date of arrival by migratory birds, dates of bird egg-laying. 

Allopatric Speciation

Population forms new species when geographically isolated from parent population.

Sympatric Speciation

A subset of popualtion forms a new species without geographic seperation.

Convergent Evolution

Unrelated species becoming more and more similar as they adapt to the same niches.

Divergent Evolution

The process of more related species becoming more dissimilar. 

Life History

A record of events related to an organism’s growth, development, reproduction and survival. 

Life History Strategy

Overall pattern in the timing and nature of life history events averaged across all of the individuals in a species 

Population Dynamics

The study of how complex interactions between biotic and abiotic factors influence variations in population size. 

Bioaccumulation

Buildup of toxic materials in food webs.

Polyploidy

When an organism possesses more than two complete sets of chromosomes, driving evolution and speciation, especially in plants.

Organisation of species

Organism

Population - Group of individuals of same species in an area

Community - Group of populations of different species in an area

Ecosystem - Community of organisms in area and the physical abiotic factora

Biosphere - Sum of all ecosystems and landcsapes

How many known species are there on the planet?

Around 1.5 million, but many, many more undescribed. 40% of insects and 25% of all animal species are beetles.