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Articles 181 - 205 of 205

Full-Text Articles in Life Sciences

Simultaneous Hermaphroditism And Sexual Selection, Eric Charnov May 1979

Simultaneous Hermaphroditism And Sexual Selection, Eric Charnov

Biology Faculty & Staff Publications

Theory about the evolution of sexual behavior in dioecious species is based on the general assumption that egg production is limited by a female's ability to garner resources to make eggs, not by a lack of sperm to fertilize them. Reproductive success for males is thus limited by access to females (and their eggs). I suggest that egg production by simultaneous hermaphrodites also obeys this principle--that fertilized egg production by an individual is not limited by sperm availability, but by resources allocated to eggs. If true, this suggests that sperm competition (reproduction success through male function) and a form of …

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The Genetical Evolution Of Patterns Of Sexuality: Darwinian Fitness., Eric Charnov Apr 1979

The Genetical Evolution Of Patterns Of Sexuality: Darwinian Fitness., Eric Charnov

Biology Faculty & Staff Publications

No abstract provided.

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Specimen Catalog & Field Notes, Elizabeth Boyd Jan 1979

Specimen Catalog & Field Notes, Elizabeth Boyd

Division of Mammals - Field Notes and Catalogs

No abstract provided.

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Sex Ratio: Adaptive Response To Population Fluctuation In Pandalid Shrimp, Eric Charnov, Daniel Gotshall, Jack Robinson Apr 1978

Sex Ratio: Adaptive Response To Population Fluctuation In Pandalid Shrimp, Eric Charnov, Daniel Gotshall, Jack Robinson

Biology Faculty & Staff Publications

Pandalus jordani is a protandrus (sequential) hermaphrodite. Populations show large year-to-year variation in age composition. In response to this variation, individuals alter the age at which they change sex. This response is predicted by a genetic model that assumes an individual shrimp maximizes its genetic contribution to the next generation.

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Facultative Sex Ratio And Population Dynamics, John Werren, Eric Charnov Mar 1978

Facultative Sex Ratio And Population Dynamics, John Werren, Eric Charnov

Biology Faculty & Staff Publications

No abstract provided.

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Evolution Of Eusocial Behavior: Offspring Choice Or Parental Parasitism?, Eric Charnov Jan 1978

Evolution Of Eusocial Behavior: Offspring Choice Or Parental Parasitism?, Eric Charnov

Biology Faculty & Staff Publications

Assuming the subsocial route towards eusociality, I show that selection favors worker habits (under haplodiploidy) provided the mutant workers are able to bias the sex ratio towards sisters and/or selectively substitute their sons for brothers. If the original workers are not able to do this, selection does not favor the habit. However, under these conditions, selection is indifferent as to whether an individual rears offspring or sibs. This makes it easy for a mother to enlist her daughters services in rearing other offspring, since the daughter cannot evolve to stop the parental parasitism. These results deal with the origin of …

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Sex-Ratio Selection In Eusocial Hymenoptera, Eric Charnov Jan 1978

Sex-Ratio Selection In Eusocial Hymenoptera, Eric Charnov

Biology Faculty & Staff Publications

No abstract provided.

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Optimal Foraging: A Selective Review Of Theory And Tests, G.H. Pyke, H.R. Pulliam, Eric Charnov Jun 1977

Optimal Foraging: A Selective Review Of Theory And Tests, G.H. Pyke, H.R. Pulliam, Eric Charnov

Biology Faculty & Staff Publications

Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by menas of mathematical models. These models are very similar, in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) - usually energy - and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; …

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When Is Sex Environmentally Determined?, Eric Charnov, James Bull Apr 1977

When Is Sex Environmentally Determined?, Eric Charnov, James Bull

Biology Faculty & Staff Publications

No abstract provided.

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Optimal Prey Selection In The Great Tit (Parus Major), John Krebs, Jonathan Erichsen, Michael Webber, Eric Charnov Feb 1977

Optimal Prey Selection In The Great Tit (Parus Major), John Krebs, Jonathan Erichsen, Michael Webber, Eric Charnov

Biology Faculty & Staff Publications

We tested the predictions of an optimal foraging model using five captive great tits as predators. The birds were presented with two prey types, profitable and unprofitable, on a moving belt. Both prey types were made out of mealworms. When the encounter rate with both prey types was low, the birds were non-selective, but at a higher encounter rate with profitable prey, the birds selectively ignored the less profitable type and did so irrespective of the encounter rate with them. These results are as predicted by the model, but the birds did not as predicted change from no selection in …

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Why Be An Hermaphrodite?, Eric Charnov, J. Maynard Smith, James Bull Sep 1976

Why Be An Hermaphrodite?, Eric Charnov, J. Maynard Smith, James Bull

Biology Faculty & Staff Publications

No abstract provided.

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Optimal Foraging: The Marginal Value Theorem, Eric Charnov Apr 1976

Optimal Foraging: The Marginal Value Theorem, Eric Charnov

Biology Faculty & Staff Publications

Science Citation Classic Award

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Ecological Implications Of Resource Depression, Eric Charnov, Gordon Orians, Kim Hyatt Mar 1976

Ecological Implications Of Resource Depression, Eric Charnov, Gordon Orians, Kim Hyatt

Biology Faculty & Staff Publications

A common but not universal consequence of the foraging activities of a predator is a lowering of capture rates with prey in its immediate vicinity. This may result from a number of different processes and need not require actual harvesting of any prey items by the predator. We term this phenomenon "depression" and its ecological consequences are the focus of this paper. A great deal of attention has been devoted to implications of changes in prey abundances as a result of the activity of predators. We will focus on changes in prey availability strictly in terms of the perspective of …

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Optimal Foraging: Attack Strategy Of A Mantid, Eric Charnov Jan 1976

Optimal Foraging: Attack Strategy Of A Mantid, Eric Charnov

Biology Faculty & Staff Publications

Much recent theoretical work in foraging theory derives hypotheses from the general assumption that animals are "efficient" in their foraging activities. Useful reviews may be found in Krebs (1973), Schoener (1971), MacArthur (1972), and Charnov (1973). The problems considered usually relate to breadth of diet (Schoeneer 1969, 1971; Emlen 1966; MacArthur 1972; Marten 1973; Pulliam 1973; Werner and Hall 1974; Timin 1973; MacArthur and Pianka 1966; Pearson 1974; Rapport 1971), strategies of movement (Cody 1971; Pyke 1974a, 1974b; Smith 1974a, 1974b), or use of a patchy environment (Royama 1970; MacArthur and Pianka 1966; Pulliam 1973; Krebs et al. 1974; Smith …

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Sex Ratio, Sex Change And Natural Selection., Egbert G. Leigh, Eric Charnov, Robert R. Warner Jan 1976

Sex Ratio, Sex Change And Natural Selection., Egbert G. Leigh, Eric Charnov, Robert R. Warner

Biology Faculty & Staff Publications

We describe the analogy between the theory of natural selection on sex ratio in newborn gonochores (which will not change sex) and on the age of sex change in sequential hermaphrodites (which are all born into one sex and change to the other later on). We also discuss the conditions under which natural selection favors sequential hermaphrodites over gonochores and vice versa. We show that, in a nearly stable population of nearly constant age composition, selection favors a rare mutant if it increases the prospective reproduction of its newborn bearers that are (or while they are) members of one sex …

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The Evolution Of Alarm Calls: Altruism Or Manipulation?, Eric Charnov, John R. Krebs Jan 1975

The Evolution Of Alarm Calls: Altruism Or Manipulation?, Eric Charnov, John R. Krebs

Biology Faculty & Staff Publications

No abstract provided.

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Hunting By Expectation Or Optimal Foraging: A Study Of Patch Use By Chickadees, John Krebs, John Ryan, Eric Charnov Oct 1974

Hunting By Expectation Or Optimal Foraging: A Study Of Patch Use By Chickadees, John Krebs, John Ryan, Eric Charnov

Biology Faculty & Staff Publications

When a predator exploits an environment in which food is patchily distributed, it has to continually make the decision of how long to stay in a patch. In this paper we examine this question using black-capped chickadees foraging in a large aviary for small pieces of mealworm hidden in artificial pine cones. The results of our experiments show the following: (a) when the birds encounter a long sequence of patches (groups of pine cones) each containing the same number of prey, they do not learn to expect a fixed number of prey per patch (Gibb's hypothesis of hunting by expectation); …

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On Clutch Size And Fitness., Eric Charnov, John R. Krebs Jan 1974

On Clutch Size And Fitness., Eric Charnov, John R. Krebs

Biology Faculty & Staff Publications

No abstract provided.

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Specimen Catalog, T. S. Byrne Jan 1974

Specimen Catalog, T. S. Byrne

Division of Mammals - Field Notes and Catalogs

No abstract provided.

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"African Catalog" And Notes, Hal L. Black Jan 1974

"African Catalog" And Notes, Hal L. Black

Division of Mammals - Field Notes and Catalogs

No abstract provided.

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Specimen Catalog, Hal L. Black Jan 1974

Specimen Catalog, Hal L. Black

Division of Mammals - Field Notes and Catalogs

No abstract provided.

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Life History Consequences Of Natural Selection: Coles Result Revisited', Eric Charnov, William Schaffer Nov 1973

Life History Consequences Of Natural Selection: Coles Result Revisited', Eric Charnov, William Schaffer

Biology Faculty & Staff Publications

No abstract provided.

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Misc. Notes Regarding Hal L. Black Collection, Hal L. Black May 1971

Misc. Notes Regarding Hal L. Black Collection, Hal L. Black

Division of Mammals - Field Notes and Catalogs

No abstract provided.

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06 September 1950 Grant County Specimen Collection Data, W.J. Koster Jan 1950

06 September 1950 Grant County Specimen Collection Data, W.J. Koster

William J. Koster Field Journals

Specimen collected 06 September 1950. Original Locality: Rio San Francisco 2 miles above Frisco Hot Spring. Locality: San Francisco River, 2.0 miles above San Francisco Hot Springs, off U.S. HWY 180, south of Pleasanton, Gila Wilderness, Gila National For
Catalog number: MSB459; Taxa: Ameiurus melas; Common name: black bullhead; Count of specimens: 2; Standard length:
Catalog number: MSB750; Taxa: Rhinichthys osculus; Common name: speckled dace; Count of specimens: 4; Standard length:
Catalog number: MSB1488; Taxa: Agosia chrysogaster; Common name: longfin dace; Count of specimens: 279; Standard length:
Catalog number: MSB2941; Taxa: Rhinichthys cobitis; Common name: loach minnow; Count of specimens: …

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08 June 1949 Rio Arriba County Specimen Collection Data, W.J. Koster, K.R. Coburn Jan 1949

08 June 1949 Rio Arriba County Specimen Collection Data, W.J. Koster, K.R. Coburn

William J. Koster Field Journals

Specimen collected 08 June 1949. Original Locality: Jemez Creek (=Jemez River)1 mile above mouth of Guadalupe Creek (=Guadalupe River). Locality: Jemez River, 1.0 mile above mouth of Rio Guadalupe, Santa Fe National Forest.
Catalog number: MSB880; Taxa: Rhinichthys cataractae; Common name: longnose dace; Count of specimens: 1; Standard length:
Catalog number: MSB890; Taxa: Rhinichthys cataractae; Common name: longnose dace; Count of specimens: 12; Standard length:
Catalog number: MSB934; Taxa: Rhinichthys cataractae; Common name: longnose dace; Count of specimens: 3; Standard length:
Catalog number: MSB1629; Taxa: Gila pandora; Common name: Rio Grande chub; Count of specimens: 1; Standard length:

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