BIOL 1020

Biology is the scientific study of how life works

• Life defies a simple, one sentence definition but is recognized by what living things do

Early formulations (and KEY players) of western science, scientific method

Reductionism

  • The scientific approach of reducing complex systems to simper components that are more manageable

Ex 1. Understanding the functioning of a tree by looking at th cells of that tree

Studying tree physiology allows an understanding of water transport at the cellular level

Inductive reasoning

  • Bacon's inductive approach included "the careful observation of nature with a systematic accumulation of data to draw upon"

Draws conclusions through the logical process of induction

Ex 1. the sun always rises in the east

Deductive reasoning

  • Deductive reasoning uses general premises to make specific predictions

For example, if organism are made of cells and humans are organisms, then humans are composed of cells

Hypothetico-deductive method (the scientific method)

Karl Popper (1902-1994) wrote: The logic of scientific discovery in 1934 in a hurry to get an academic post outside of nazi run eurpoe

Steps of Hypothetico-deductive method

1. Identify a broad problem statement

2. Define a problem statement

3. Develop hypotheses (best guess)

4. Determine measures necessary to test prediction

5. Data collection

6. Data analysis\

7. Interpretation of data ( does data fit with your hypotheses and predictions?)

Darwin used mostly observations, also artificial breeding experiments. Most early biologists were

ardent and skilled

What should we know about monarchs to understand decline

• We need to understand their natural history

Types of Data

Data are recorded observations or items of information, these fall into two categories:

  • Qualitative data or descriptions rather then measurement
  • Quantitative data using measurements and numbers; often organized into tables and graphs and because they are often variable, analyzed with statistics and come in various forms.

The 4 ways of knowing ways of thought in Western SCience are

Inductive reasoning, reductionism deductive reasoning and the hypothetico deductive method

Population of ecology

Definition of a population:

Populations includes all individuals of a single species that live and reproduce in a particular place

Human demographers think about human populations, but biologists generally think about animal and plant populations. the study of which is also called demography.

For animals or plants that are sedentary: survival and reproduction occur in the same place so simplifies the definitions of populations

Mobile animals: populations need additional adjectives: non breeding, migratory, breeding Examples:

Migratory birds, caribou, insects, fish

Key features of populations:

• Population size

• Geographic range

• Population and density and distribution

  • Density is always expressed as numbers per unit area (often ha, but could be km squared or any other area unit)
  • Populations can be spread out or concentrated
  • Pattern can also vary even with same density
  • Density is not to be confused with abundance

The simple method has a number of assumptions:

1. Population is closed

2. Each butterfly whether it is marked or not has an equal probability of capture

Complications: counting individuals in plant populations

Foundation of population biology

Births=deaths

If births > deaths then population should increase

If births < deaths then population should decline

Population decline or growth

• Affected birth, death, immigration and emigration

• Also want to know rate of increase or decrease

• Ex population starts at 80 individuals, after two years increases to 120 individuals rate of increase-40/2=2 per year ( relatively rapid)

• Rmax and its relationship with body mass: the bigger the organism, the lower the intrinsic rate of

increase

Ecological niche: fundamental and realized

What is a niche:

• "N-dimensional hyperspace" (Hutchinson 1957)

• Or, less formally: A species's place in nature

Niche vs. habitat

A niche refers both to where it occurs and what they do there (eg. filter water, eat tadpoles, absorb light) that is the way that organisms respond to and also affect the resources and other species in the habitat

Habitat is where a species lives (eg. open sandy beaches, rocky intertidal zones, mountain cliff)

Fundamental niche includes all the habitat potentially available to a population

Niche partitioning. can be temporal (varying across time) or spatial

Temporal partitioning: in grassland ant assemblages

Spatial partitioning: in dinosaurs. Mudstone= black, sandstone grey

Classic examples of niche partitioning in Dominican republic anolis lizards

Diet (or one dimension of their niche) is broadly similar (eg. insects and other arthropods) but they separate among tree strata

New Anolis on lichen covered branches discovered in 2016.

The role of evolutionary history in the niche of an organism:

  • Groups of species within the same family or order will have relatively similar niches because they have all evolved from a common ancestor( phylogenetic niche conservatism)

But NOT always and not exactly:

  • Carabid beetles (the GROUND BEETLES) have really diverse niches even within the same family (carabidae)

Take home: attempts to manage or mitigate losses often means treating each species separately

Phylogenetic niche conservatism would explain why?

  1. All marsupials raise young in a pouch
  2. All bears are carnivores
  3. Most ferns live in wet or damp places
  4. All insectivorous bats use the three dimensional air space for foraging
  5. All of the above

Contrast inter-and intraspecific interactions

Tip: how to remember the difference:

Think: international means more than one nation, so interspecific interactions means interactions between two or more species

Characterizing interactions (examples)

  • Predation: positive for predator and negative for the prey, effect on survival and reproductions of predator, negative effect on survival and reproduction on prey
  • Mutualism: Positive Positive meaning its positive for both species that interact
  • Survival+reproduction= fitness

Competition: (-/-)

• Two forms: Interference and exploitative

• Interference competition is direct physical competitions for resources between individuals

• Exploitative competition: is indirect, when one species reduces resources for the other (shared resources)

Competitive Exclusion:

• Gause (1934) first proposed this concept

• Two species competing for the same limiting resources cannot coexist permanently in the same place

• Even a slight reproductive advantage through more efficient feeding, reproduction will eventually lead to local elimination of the inferior competitor

Practically:

Because species have their own ecological niche, it is rare to see competitive exclusion in the

wild (at least between two co-existing native species that have been separated for a relatively long

time)

• The only way really to test it is through removal experiment

BUT... rejection of hypothesis that competition explains distribution is difficult

  • The ghost of competition past may have sorted out of differences in evolutionary time to AVOID competition
  • Sometimes similar species can have similar niches but having diverged in recent past, now hybridize, threatening the existence of one of both species

Predation (+/-)

  • Predators have an acute sense that enables them to find and identify orey. Ambush predators are disguised, pursuit predators fast and agile
  • Prey have similarly acute senses and special adaptations to help them avoid being eaten
  • Through natural selection there is an arms race between predators and prey
  • Mimicry is also used by some predators
  • Partial predation: Eg, a bird lays 14 eggs only 9 get eaten

Whereas predation accounts for most of the mortality in vertebrates and natural selection favours those who survive

Herbivory: the term is used when an organism eats part or all of a plant

Specific adaptations:

  • Canada Geese (Branta canadensis) with a more delicate bill, graze like cows
  • Snow Goose, with their more robust bill
  • Special sensory organs (eg, chemical sensors on feet of insects), specialized digestive systems (eg, ruminants) and teeth

Anti herbivory adaptations

  • Secondary compounds/metabolites: broad name for chemicals that protect plants against herbivory (among other potential functions)
  • Structural protection: Without herbivores: Galapagos Opuntia

Varying definitions of symbiosis

  • 2 species living together and one can benefit or they both benefit
  • Plant bird mutualism: Many species of plant depend on bird herbivory to both disperse thor seeds and often germinate them
  • Unlike predation, parasites usually do not kill their hosts

Measuring biodiversity if the community

  • The simplest is species richness
  • Can be measured at different scales, the province
  • There are a variety of measures that weight different species differently because many communities have a relative abundance pattern

What does H mean

• Higher numbers mean habitats with more species and more even distribution of species

• Comes from information theory: early computer science

• Rare species do not contribute much to the functioning of the ecosystem

Energy

  • From the base of plant productivity about 10% of the biomass of each trophic level is passed on to the next higher level

Predation

  • Disturbance (+) but intermediate levels usually correspond to conditions with most species
  • Classic experiment: Removal of star fish from intertidal sites in Washington state (Paine 1974)
  • Ecological succession (=effect of time): defined as the sequence of community and ecosystem changes after a disturbance. Usually older stages have fewer species
  • As succession occurs species move from R-strategies to K-strategists Island biogeography: effect of island size on biodiversity

Summarizing area effects

  • Species richness in many island habitat increases with area of the island
  • Can apply principle to terrestrial island or patches